php|architect (October 2003)

OCTOBER 2003 VOLUME II - ISSUE 10 The Magazine For PHP Professionals Migrating from MySQL to PostgreSQL Reasons and c...

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OCTOBER 2003

VOLUME II - ISSUE 10

The Magazine For PHP Professionals

Migrating from MySQL to PostgreSQL Reasons and considerations An Introduction to GD Dynamic image creation and manipulation with PHP

Integrating PHP in Delphi Applications Open new worlds with the php4delphi component

Calendars with PHP Using the Calendar extension

www.phparch.com

Introduction to Statistical Charting using PHP Foiling Cross-Site Attacks

Get Ready For php | Cruise See inside for details

March 1st - March 5th 2004

Plus: Tips & Tricks, Product Reviews and much more...

This copy is registered to: Liwei Cui [email protected]

In partnership with Zend Technologies

Zend Studio 3.0 is the official PHP IDE of php|cruise

We’ve got you covered, from port to sockets.

php | Cruise

Port Canaveral • Coco Cay • Nassau

March 1st - March 5th 2004 Signup now and save $100.00! Hurry, special offer ends October 31st.

Visit us at www.phparch.com/cruise for more details. Andrei Zmievski - Andrei's Regex Clinic, James Cox - XML for the Masses, Wez Furlong - Extending PHP, Stuart Herbert - Safe and Advanced Error Handling in PHP5, Peter James - mod_rewrite: From Zero to Hero, George Schlossnagle - Profiling PHP, Ilia Alshanetsky - Programming Web Services, John Coggeshall - Mastering PDFLib, Jason Sweat - Data Caching Techniques Plus: Stream socket programming, debugging techniques, writing high-performance code, data mining, PHP 101, safe and advanced error handling in PHP5, programming smarty, and much, much more!

TABLE OF CONTENTS

php|architect Departments

Features

9 5

Migrating from MySQL to PostgreSQL EDITORIAL

by Rick Morris

I N D E X

17 6

Introduction to the Calendar Module

WHAT’S NEW

by Eric Brown

50

PRODUCT REVIEW

24 Using the GD library with PHP

Zend Studio 3.0

66

TIPS & TRICKS

by Pavel Koutny

39 Integrating PHP into Delphi Applications

By John W. Holmes

by Toby Allen

70

BITS & PIECES Real. Interesting. Stuff.

53 Foiling Cross-Site Attacks by Chris Shiflett

72

exit(0); Digital Monopoly By Marco Tabini

59 Introduction to Statistical Charting using PHP by David Jorm

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EDITORIAL

E D I T O R I A L

R A N T S

P

HP’s maturity is beginning to show. Frameworks are becoming numerous and varied, design patterns are appearing, standards are emerging. There is still much to be done, and some big questions to be asked (and answered), though. Every time I see a new framework announcement, I cringe a little bit. I’m reminded of a blog entry on www.artima.com in July of this year*. It talked about the “competition” between open-source projects (Perl vs. Python or MySQL vs. PostgreSQL, for instance), and how “...huge amounts of talent and energy are being wasted duplicating in one language functionality that is already available in one or two or three others, simply because of the almost religious fervor with which the devotees of the various open source languages, tools and platforms seek to prove the superiority of their own particular chosen technologies...” Developers are a stubborn, arrogant, and egotistical bunch. At least I am. When I started seeing the need for consolidation of techniques at my day job, I probably could have used almost any pre-existing framework, but I created my own. It wasn’t necessarily because I thought I could do it better, but really because I just wanted to do it. It gave me a great sense of pride and satisfaction (until I had to maintain it!) to see my framework being used for lots of different projects in the company. Often, people would sooner write their own API than take the time to learn somebody else’s. This, like the above quote states, is just a huge waste of talent and energy. Imagine the quality of the libraries that could be created if each of those talented people developing frameworks was actually contributing to a single project. I feel the same way about IDE’s. WeaverSlave, PHPEdit, Zend Studio, etc—they all have features that I like, but not all in one place. Maybe a “single” project is not reasonable, but PEAR has made strides in this area—especially with the PFC. Cooperation should be the goal, not competition. Enhancement of the community, not expansion of your ego. And that’s all I have to say about that... Returning to the present, although the web arena is still in its adolescence, PHP is less than satisfied with being a simple server-side language. The pace at which new (and sometimes crazy) applications for PHP are popping up has increased dramatically recently. But why shouldn’t they? According to the Netcraft-sourced usage graph at www.php.net/usage.php, PHP has gained ~5 million domains in the last year, compared to ~2 million the year before. It would also make sense that PHP is also the most popular** Apache module—by a very wide margin. As PHP4’s days become numbered, and PHP5 materializes, these statistics will almost certainly take another jump. PHP will further penetrate the “enterprise”,

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Volume II - Issue 10 October, 2003

Publisher Marco Tabini Editor-in-Chief Peter James [email protected] Editor-at-Large Brian K. Jones [email protected] Editorial Team Arbi Arzoumani Peter James Peter MacIntyre Brian Jones Eddie Peloke Graphics & Layout Arbi Arzoumani, Martina Rosati Managing Editor Emanuela Corso Director of Marketing J. Scott Johnson [email protected] Account Executive Shelley Johnston [email protected] Authors Toby Allen, Eric Brown, Peter James, David Jorm, Pavel Koutny, Rick Morris, Chris Shiflett php|architect (ISSN 1705-1142) is published twelve times a year by Marco Tabini & Associates, Inc., P.O. Box. 3342, Markham, ON L3R 6G6, Canada. Although all possible care has been placed in assuring the accuracy of the contents of this magazine, including all associated source code, listings and figures, the publisher assumes no responsibilities with regards of use of the information contained herein or in all associated material.

Contact Information: General mailbox: [email protected] Editorial: [email protected] Subscriptions: [email protected] Sales & advertising: [email protected] Technical support: [email protected] Copyright © 2002-2003 Marco Tabini & Associates, Inc. — All Rights Reserved

EDITORIAL

S T U F F

and start to garner the sort of respect from corporate entities that community leaders have been fighting for since at least PHP4’s inception. PHP developers—both internals hax0rs and users—are finally coming of age with their crafts, and this naturally leads to excellence, creativity, and new directions. When a people no longer have to worry about finding their food, they start to think about how to cook it differently. This is the force that drives innovation. We at php|a work hard in many ways to keep you informed of these new directions—in our daily news, our What’s New! column, our Bits and Pieces column, and our articles. For innovative new directions this month, we look to the php4delphi component. Some inventive folk have put together this Delphi component that effectively embeds the PHP scripting engine into your Delphi application. Also, check out Bits and Pieces for information on client-side PHP, and What’s New! for a fix of recent releases. Next month will feature introductions to SQLite and PHP-GTK, both of which have represented bold steps for PHP and for the community. There’s never a dull moment in this community, and we’re glad we can be part of it. I hope you enjoy this month’s issue. Besides the php4delphi component article mentioned earlier, the

*www.securityspace.com/s_survey/data/man.200309/apachemods.html **www.artima.com/weblogs/viewpost.jsp?thread=7351

php|a

What’s New! PHP 4.3.4 RC1 PHP.net announced the release of PHP 4.3.4 RC1 “This release candidate contains only bug fixes, so it should be quite stable. Please test this release as much as possible, so that any remaining issues can be uncovered and resolved prior to the final release.“ Changes in this release include: • Made MCVE extension available on win32. • Added apache_get_version() function.

N E W

issue also sports an excellent introduction to GD, a database migration article that is sure to push some buttons, a great article on doing statistical calculations and graphs in PHP, a very detailed article on cross-site attacks, and a solid introductory article to the Calendar functions. As always, I look forward to hearing from you at [email protected] or in the forums.

• Fixed disk_total_space() and disk_free_space() under FreeBSD. • Fixed crash bug when non-existing save/serializer handler was used. • Fixed memory leak in gethostbynamel() if an error occurs.

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• Fixed FastCGI being unable to bind to a specific IP. • much more... Get more information or download from PHP.net. PhpEd 3.2.1 NuSphere Corporation announces the release of PhpED v3.2.1, which is a major update for version 3.2. NuSphere phpED is an IDE (Integrated Development Environment) that integrates a comprehensive set of editing, debugging and deployment tools for PHP scripting language. The version is available for Windows or Linux machines. The changelog can be seen here. The trial version of PhpED is available for immediate download from: http://ww1.nusphere.com/web/

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NEW STUFF

Komodo 2.5 Komodo 2.5 has been released form ActiveState.com. ActiveState.com describes Komodo as: ”the award-winning, professional integrated development environment (IDE) for open source languages, providing a powerful workspace for editing, debugging and testing your applications. Komodo offers advanced support for Perl, PHP, Python, Tcl, and XSLT.” Get more information or download a trial from ActiveState.com

MySQL.com announces the release of MySQL 4.0.15. MySQL 4.0.15, a new version of the popular Open Source/Free Software Database, has been released. It is now available in source and binary form for a number of platforms from our download pages at www.mysql.com/downloads/ and mirror sites. This is a bugfix release for the current production version. Get more information from MySQL.com

Tidy 0.7b Coggeshall.org announces the release of Tidy 0.7b. “The tidy extension version 0.7 beta has been released and boasts a lot of major changes! These changes include the patches provided by Illa (which I already told you about) as well as a complete re-write of the PHP 5.0 specific HTML Parsing routines. This re-write makes them much more stable, and I encourage you to check them out!” You can get more information or download from Coggeshall.org.

Turck MMCache PHP accelerator Freshmeat.net announces the release of the Turck MMCache PHP accelerator, encoder and optimizer version 2.4.0. The release claims

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Turck MMCache will typically increase the speed of PHP code by 1-10 times. Changes in this version include “Support for incomlete classes in mmcache_get() was implemented. The PHP version is now checked. A problem with include and include_once under PHP 4.3.3 was fixed, along with the improper “Cannot redeclare ()” error and an issue with caching files under Windows when given absolute paths but not drives. This release was tested with PHP 4.3.3 and php5-200309021330” Get more information from Freshmeat.net.

LiteSpeed Web Server 1.0.4b Beta LiteSpeedTech.com announces the release of LiteSpeed 1.0.4b2 Beta. What is LiteSpeed? “LiteSpeed Web Server is a full-featured, high-performance, secure, and easy-to-use Web server that runs on Unix and Linux. It supports HTTP/1.1, SSL, CGI, FastCGI, PHP, JSP, Servlets, GZIP compression, IP level throttling, connection accounting, DoS attack prevention, and instant recovery mechanisms. Installation is very easy with pre-built binary. Administration and configuration is very easy through a Web interface.“ According to the LiteSpeed site, some of the changes in this release include: “Added .htaccess support; added .htaccess cache; Apache like authentication, access control and redirect directives were supported in .htaccess” Get more information or download from LiteSpeedTech.com

PHP Frameworks Sitemanager 2.5.2 Roadsend.com announces the release of Roadsend PHP SiteManager 2.5.2. What is it? According to the Roadsend homepage: ”SiteManager is an Open Source Web Application Framework written in PHP. It was designed to help PHP programmers and development teams separate the process of web site design into four steps: code creation, layout design, site implementation and site management.” Get more information or download from http://www.roadsend.com/siteManager

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NEW STUFF

Zend Studio 3.0 Zend.com announces the release of Zend Studio 3.0.

PHP Seagull 0.3.1 Beta PHPKitchen.com announces the release of the PHP Seagull Framework 0.3.1 Beta. This release of the Seagull framework offers the following improvements:

• Code Analyzer - Create robust, secure applications using Zend’s code analyzer, which analyzes static source code and attempts to reconcile problematic code. Locate unreachable code, variables or objects that have been defined but not used or empty variables.

Get more information from PHPKitchen.com

InterJinn The php|architect forums bring news of a new PHP Framework, Interjinn. What is it? InterJinn.com describes it as:”an open-source multitier framework for web and shell applications using the PHP scripting engine. Focus lies on web development and with that in mind the InterJinnTM framework provides the following integrated features:

or

download

• One Click Browser Direct Debugging Revolutionizing the concept of debugging and profiling by allowing you to easily debug and profile directly from your browser. Quick installation of the One-click Browser Direct Debugger toolbar on your browser allows you to automatically start debug sessions directly from your browser. (Currently only supports Internet Explorer Browsers. Mozilla support will be released shortly.) • PHP 5 support - Advanced editing, debugging and analysis of PHP 5 applications including syntax highlighting, code completion and file and project inspectors for new PHP 5 syntax. • Code Completion Improvements - The most robust code completion available is now faster, recognizes constants, and includes a new functions arguments view. • Support for JavaScript and HTML- Syntax highlighting and code indentation support for JavaScript and HTML.

session management profile management run-time component binding run-time property binding caching mechanisms form engine with advanced validation customizable templating system multilingual resolution “

Get more information InterJinn.com.

Zend Studio 3.0 is a major release and includes new features for developing and debugging PHP applications. • Profiler - Determine which parts of the application are slowing down your project so you can focus your time on improving the overall performance of your applications.

• cleaner organization of modules and admin options • new block manager • a navigation manager, ie a wizard to create dynamic site navigation • overhauled error handling with a new session debug feature • easier configuration • improved database abstraction bringing PostgreSQL and SQL Server compatibility a step closer

• • • • • • • •

What’s New?

• Real time Syntax-Error highlighting - Immediately find syntax errors as you type. The Syntax Error Indicator bar pinpoints syntax error location within file. • Performance Improvements - Significant performance improvements both at launch and run-time.

from

• Many bug fixes and improvements For a limited time only, you can buy the Zend Studio 3.0 (both Basic and Plus editions) from the php|a store and save 10% off the retail price. Visit our product page for more details: (http://www.phparch.com/shop_product.php?itemid=5).

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8

Migrating from MySQL to PostgreSQL by Rick Morris

F E A T U R E

Is there a reason to migrate? Is there a right time and a wrong time? What is the best strategy for migration?

The Reason If you have been a developer for any time at all, you have probably come across a situation which could be described as “project sprawl”. You started a project as a nice simple compact application, and before you know it, your company/client wants the application to handle far more than you ever imagined. Suddenly you are faced with reporting needs, integration with other software, data importing, etc... So it’s happened to you: your PHP/MySQL web application that you put together hastily 2 years ago has gradually turned into a company’s mission-critical application. Kudos to you... but, some things are starting to happen that have you worried: 1. You are noticing certain unexpected problems occurring with your data. People input things you didn’t plan for, or they update the wrong combination of tables, and due to a marginal bug in your PHP code, when they try to roll back that update, not all the data is erased. 2. The company starts coming up with more and more requests for extending the system in ways you hadn’t anticipated. Face it—as creative as programmers can be, users often come up with more creative ways of connecting things than you ever expected. Why not? It’s their business. They want all sorts of

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things to just happen automatically, without any user intervention. (“When the commissions are higher than $500, I want an extra 5% to go to the sales manager, and when the total commissions are more than $50,000 for any month, I want a special report mailed to me...”) 3. The company’s Visual Basic development team has been making noises about connecting to your data. Up until now, they have been importing the data into their historic Access database every day for back-end accounting and reporting. But of course, the accounting department has complained enough, and gotten the OK to modify your data too. In fact, everyone in the business actually prefers your data model, and they want to consolidate all the company data in one place. 4. Also, someone doing some Java development for another web application is hoping

REQUIREMENTS PHP: 4.0+ OS: N/A Applications: N/A Code: http://code.phparch.com/16/1 Code Directory: postgres

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Migrating from MySQL to PostgreSQL

to connect to the data. Between this and the VB application, you are starting to get nervous. Because all your application constraints have been painstakingly developed in PHP, how will you make sure that each of the other applications also behaves by those rules? Not fun... In fact, this is quite an impossible task if there will be other development teams accessing your data. It’s time to move the business logic into the database, or run laughing madly into the night. Your choice. In order to make this sort of change, for the present “MySQL has you will have to give up provided a working with MySQL. generation of Hopefully, in the future, these features will be presdevelopers ent in MySQL, but there is with an easy another open-source DBMS that has been working well way into datawith PHP all along: base-backed PostgreSQL. In fact, programming...” PostgreSQL has quite an interesting history as an open-source project, coming from the halls of Berkeley right alongside Unix itself. And, to be fair, there are other excellent open-source systems that have these features (such as Interbase/Firebird and SAPDB), but in my opinion none of them have been as consistently developed through the years. MySQL is a special case in the database world. It is the only popular SQL DBMS that doesn’t support logical abstraction and database-wide constraints with views, user-defined functions and triggering mechanisms (in fact, even MS Access supports more of these features than MySQL). It has, however, provided a generation of developers with an easy way into database-backed programming, offering a short learning curve and easy installation on many platforms. If you have spent any time browsing the endless newsgroup discussions and forum threads about database-backed programming, you realize that there is a basic subtext to the difference between a lightweight DBMS like MySQL and an enterprise-class DBMS like PostgreSQL: with one, you enforce constraints and business logic in your application code; with the other, you handle constraints and a good part of the business logic in the database. Yes, MySQL has been making progress in these areas, but there is much more ground to cover. The question is not whether one is right or wrong, but exactly where you want to focus your efforts for the most gain in a given situation. It is understandable that one would do simple stand-alone applications without worrying about database-level constraints and abstrac-

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tion, but that game quickly becomes tedious (even dangerous) when faced with large multi-layered applications, or data that must be shared between environments. Just like an object-oriented framework can assist in insulating different areas of your application, abstraction via views, constraints and procedures can insulate the persistence layer (your database) from disaster, as well as provide better encapsulation of your data logic. So, given the scenario above, you might decide it’s finally time to migrate to a DBMS with enterprise SQL features. We’re not just talking about transactions here; we’re not just talking about foreign key constraints; we’re talking about database-wide control over exactly what happens, in what relationship, and when it is allowed to happen. In fact, we are talking about the ability to automate things behind the scenes, so the application layer doesn’t even need to “know” what goes on. Some examples of PostgreSQL features, and the resulting benefit: 1. Views: Create a view from a complex query; no one else needs to worry about those details, they just do simple queries from that view. CREATE VIEW customer_last_purchase AS SELECT customer.compname, invoice.invnum, invoice.amount, MAX(invoice.orderdate) as last_purchase FROM customer, invoice WHERE customer.cust_id = invoice.cust_id GROUP BY customer.compname, invoice.invnum, invoice.amount, invoice.cust_id ORDER BY customer.cust_id, MAX(invoice.orderdate);

2. Column and table-level constraints: These are not limited to primary keys, foreign keys, and NOT NULL, as with MySQL. CREATE TABLE invoice_detail( detail_id SERIAL NOT NULL invoice_id INT REFERENCES invoice(invoice_id), price NUMERIC(10,2) CHECK ((price >= 0), quantity INT CHECK ((quantity % 5) = 0), discount INT CHECK (discount IN(0,5,10,15)) CHECK (price > (discount * 10)) );

3. User-defined functions: Ever wanted to stick some complicated piece of programming logic into a query? With PHP/MySQL programming, you might handle that with PHP, such as $time_interval = complex_calc(mktime(0, 0, 0, ); date(“m”) - 1, date(“d”), date(“Y”)), $status) $result = mysql_query(“SELECT * FROM accounts_rec ); WHERE aging = ‘$time_interval’”)

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With PostgreSQL you can keep all that logic in the database: SELECT * FROM accounts_receivable WHERE aging=complex_date_calc(now());

This way PostgreSQL provides all programmers and programming environments the ability to share that logic with no difficulty at all. 4. Event-based logic: PostgreSQL provides for methods to respond to any UPDATE, INSERT, DELETE or even SELECT statement on any table or view in your database. This is accomplished with the following two mechanisms: a. Triggers: These allow you to “intercept” any UPDATE, INSERT, or DELETE on any database object, passing the event data along to be handled by a user-defined function (see point 3, above). Triggers can be set to fire before an event, after an event, or instead of the event. CREATE TRIGGER log_update AFTER UPDATE OR INSERT ON userinfo FOR EACH ROW EXECUTE PROCEDURE log_update();

A trigger can be used to simply add logic to a query, or to completely replace the intended query with another action internally. For example, every DELETE that occurs in your “customers” table could result in that data being archived in a “customer_archive” table, while an update could archive the last snapshot of the data for versioning. Note that with PostgreSQL, a function must be defined before you create a trigger. b. Rules: These allow you to simply rewrite a query internally, much like Apache’s mod_rewrite allows you to rewrite URL requests coming into the webserver. (Note that a separate rule must be defined for each event, such as DELETE, INSERT, SELECT) CREATE RULE log_update AS ON UPDATE TO userinfo DO INSERT INTO userinfo_log VALUES (NEW.username, NEW.email, current_user, current_timestamp);

This method has two interesting advantages: first, it doesn’t require an external function—

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you simply rewrite the SQL as part of the rule definition; second, it can respond not only to actions that modify data, but even to a SELECT query. In fact, the RULE system is how PostgreSQL accomplishes many internal tasks, and is the method used to provide for view updatability. In fact, since view updatability is defined explicitly in a rule, any additional logic can be added to the queries that modify data in a view. What all this amounts to is a drastic reduction in the amount of complex SQL code visible in the application, and a greater decoupling of the application and persistence layers. The Right Time or the Wrong Time Yes, this is all well and good, but is it really worth it to move to PostgreSQL? To assess this, we need to find out the purpose of the migration. Which of these categories do you fall into: 1. You are migrating to PostgreSQL just because you heard it is better: Then you really need to decide whether you are going to take the time to learn its features. These features are similar on almost all ANSI SQL systems, so this experience will stand you in good stead anywhere, even with Oracle; but if you plan to use PostgreSQL exactly the same way you used MySQL, then what’s the point? 2. You decided that you need foreign key constraints and transactions: If that’s all you want, then just upgrade to the latest version of MySQL, and convert your tables to the InnoDB type. Foreign key constraints are an important addition to MySQL’s feature set, and it is good that MySQL users finally have this option, but foreign keys alone won’t guarantee your data integrity across application environments. 3. You don’t know where your data will end up, but you want to keep your options as open as possible, including a possible future move to an enterprise-class commercial DBMS such as Oracle or Sybase. If that’s the case, then rest assured that PostgreSQL’s nearly-complete ANSI-92 and (approaching) ANSI-99 compliance will make it much easier to move between systems. MySQL has chosen many non-standard approaches to querying and data manipulation, which don’t translate easily to other systems.

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4. You have been reading about the concepts of true relational database design, and the idea of preserving the business logic in your database, and you realize this is appropriate for your project(s): Then you are a class-A candidate for PostgreSQL migration, because it can handle any of those needs. Let’s imagine a specific example. The application you developed was a CRM-type application used to track contact with customers. Your company management wants to keep track of each step in the process of serving customers. As each stage in the relationship occurs, they want different screens and notices to appear in your application. Of course, it is important for them to know what the elapsed time was at each stage. How long did it take for the sales team to contact the prospect after receiving the sales lead? How long from the time of first contact to the acceptance or rejection of the service? What was the average response time? How many calls did it take before establishing contact with the prospect? Up until now you have handled all of that logic in PHP, mainly with if/then/else or case/switch statements. After all, you knew exactly when each of these events occurred in your system because PHP was doing all the inserts and updates. Now that VB and Java programmers will be accessing this data, and even updating it, you are wondering how best to enforce this business logic. Since these time intervals are very important to the company’s statistical analysis team, you had to build extensive reports on them. There are important “milestones” in the list of events you maintain for customer contact. At first, you simply maintained a flat list of events, with a timestamp and an “event_type” attribute, but you found that querying that table for several different intervals between several different types of events for each related customer account quickly grew unwieldy, so you now are maintaining the intervals in a separate table, expressed as seconds. Of course, this also means that you now have to do yet another insert during each event. With MySQL, this is yet another level of complexity that will have to be handed around to the different application layers. In PostgreSQL, you simply define an on-insert trigger or rule to handle the intervals table, and let the application go its merry way. There is a hidden benefit to this approach also: you just accomplished 2 steps with one database call from your application. This is especially helpful for performance if your application server must connect to the database server over the network. In fact, sometimes you can accomplish many steps in the database backend, resulting from only one query on the application side:

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SELECT my_procedure(‘parameter1’, ‘parameter2’,’parameter3’, [etc...]);

You only call one query, but ‘my_procedure’ handles all kinds of database-specific logic on the other end. Think about it this way: at any step or action, once the application hands off its data to the database, it should be free from concerns about how the database handles that data. This way, you have a perfect separation of concerns. The application programmers do what they do in order to present the choices to the user, get user input, and send it off to the database, while the database handles the “making sure” stuff. So now you’re convinced that you need to migrate. How hard is it? Well, there’s good news, kind-of good news, and bad news: 1. The good news: Generally, since PostgreSQL supports more features than MySQL, there are no complicated workarounds needed to move to PostgreSQL, whereas you would need plenty of application-level workarounds to move in the other direction. 2. The kind-of good news: PostgreSQL is a little more strict about how it handles your data (this is a Good Thing), but that means there will be some work needed to fix data that MySQL allowed but PostgreSQL thinks should NOT be allowed; for example, MySQL allows incomplete data in a date field, and also automatically processes “questionable” conversions, such as truncating integers as they are inserted. (How can this be good news? It’s good news because you will be moving to a system which handles these things better.) 3. The bad news: There are quite a few differences in syntax between MySQL and PostgreSQL, especially with such areas as text-manipulation functions, date/time formatting, etc... Also, there are differences in the PHP functions used to access the two systems. While it would be nice if it were just a matter of searching your PHP codebase and replacing every instance of mysql_[whatever] with pg_[whatever], it’s not going to be that easy. A Strategy for Migration Unfortunately, migration from MySQL to PostgreSQL is not a painless operation at present. It is still worthwhile, though, for the benefits you get with PostgreSQL. First, you need to install PostgreSQL. It is mainly a

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Unix-centric DBMS, but it is definitely possible to run it on Windows with the Cygwin Unix emulation toolkit. Currently, this is only good for development, though, not production. The next major release of PostgreSQL (7.4) should include a native Windows binary which will perform extremely well. As for the difficulty of installation on *nix systems, even an install from source is no more difficult than pasting the lines in Listing 1 into your terminal. Listing 1 ./configure gmake su gmake install adduser postgres mkdir /usr/local/pgsql/data chown postgres /usr/local/pgsql/data su - postgres /usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data /usr/local/pgsql/bin/postmaster -D /usr/local/pgsql/data >logfile 2>&1 & /usr/local/pgsql/bin/createdb test /usr/local/pgsql/bin/psql test

Now comes the data conversion. There are two attempts at a conversion utility: “my2pg.pl” and “mysql2pgsql”, which are located in the ‘contrib’ section of the downloaded PostgreSQL source. These are just simple Perl scripts which attempt to take a dump from MySQL, and use some text processing to make the table definitions and data fit PostgreSQL. Unfortunately, I believe these scripts are nowhere near being up-todate (my2pg.pl is more recent than mysql2pgsql, though). Really, at present the only way to do a true conversion is by hand, manually checking the column types and understanding the differences between how the two systems define things. Here are some of the major differences:

refer to the standard ‘YYYY-MM-DD HH:MM:SS’ format for SQL dates. So, if you are storing Unix timestamps in MySQL, you will have to store those in an INT column in PostgreSQL, while datetime values in MySQL will have to be “cleaned up” and stored in a PostgreSQL timestamp column. 2. PostgreSQL doesn’t have TINYINT or MEDIUMINT. The three main integer types in PostgreSQL are SMALLINT or INT2 (+32000), INT or INT4 (same as MySQL’s INT, except cannot be ‘unsigned’), and BIGINT or INT8 which allows for extremely large integers, even on a 32-bit system. Since INT cannot be unsigned in PostgreSQL, you will have to use a CHECK constraint or some other method if you don’t want a column to go negative. (Or, since PostgreSQL supports user-defined types, you could just create an ‘unsignedint’ type of your own) 3. Auto-increment works differently. PostgreSQL uses sequences, which allow more control and flexibility. Fortunately they provide an easy shorthand for creating an auto-incrementing field (serial): CREATE TABLE mytable( id SERIAL, othercolumn VARCHAR(24) etc... );

4. PostgreSQL doesn’t have the ENUM column type. Where MySQL might use: mycolumn ENUM(‘yes’,’no’,’maybe’)

1. MySQL’s datetime columns allow storage of incorrect dates; for example, if one inserts an empty string or a 0 into a datetime column, MySQL accepts it, and enters ‘000000-00 00:00:00’. This is obviously incorrect, because there is no zero month of the year, nor is there a zero day of the month. Also, MySQL allows for all months to have 31 days, even February. Many MySQL databases are full of these sorts of values, which will not be accepted by a PostgreSQL timestamp column. Here is the other area of confusion. In MySQL ‘timestamp’ is really just an integer column holding a Unix timestamp, in seconds. PostgreSQL does not store a Unix timestamp, but uses the term ‘timestamp’ to

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PostgreSQL could achieve a similar result as follows: pgcolumn VARCHAR(5) NOT NULL CHECK(mycolumn IN(‘yes’,’no’,’maybe’))

This uses a CHECK constraint to prevent the VARCHAR column from having anything except those 3 values. 5. PostgreSQL doesn’t have the SET column type. The SET type in MySQL is an odd one. It’s not really a SET, it’s not quite an array; it’s really a comma-delimited list of strings, which can be toggled on or off as a bitmask. Notice that you cannot even have an

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escaped comma in one of the list values. Some would even say that the MySQL SET type is a bit of a hack, best to be avoided. Where MySQL might have: mycolumn SET(‘one’,’two’,’many’)

PostgreSQL might be able to use the Array type, which is a full-featured multi-dimensional array implementation: pgcolumn VARCHAR[3] CHECK( (pgcolumn[0] = ‘one’) AND (pgcolumn[1] = ‘two’) AND (pgcolumn[2] = ‘three’))

The above column definition would create an array with 3 elements, and constrain those to be either NULL or to have the value desired. But PostgreSQL doesn’t really limit the size of an array, so it’s not quite possible to get the same features here without some more logic, which we won’t bother with at the moment. Really, the problem of a SET type is much deeper

“Test, test, test. Don’t expect to migrate live data without testing.”

than this, and involves thinking more deeply about database design. For most database purposes, the best advice is to use proper normalization techniques, and create a separate table to hold all these values; for example, one could just create a table with boolean columns for each value: CREATE TABLE my_bitmask ( one bool NOT NULL, two bool NOT NULL, many bool NOT NULL );

Then you could just use a foreign key constraint to tie these values to the table in question. It’s also much more flexible if you need to change your data model in the future. 6. There are quite a few differences in querying and data manipulation. Again, MySQL uses many non-standard approaches to syntax, and if you have used many of them then you will have to convert queries in your application before migrating (Table 1 and 2). There are plenty of other small differences to be aware of, especially in how text-manipulation functions work, so you will have to review any query that uses these kinds of methods. To perform your PostgreSQL migration more easily, do the following:

Table 1: SQL syntax differences between MySQL and PostgreSQL.

MySQL

PostgreSQL

REPLACE INTO tablename

DELETE FROM tablename; INSERT INTO tablename;

IF ... THEN... ELSE

CASE WHEN ... THEN ... ELSE ... END

CONCAT([value1], [value2], etc...)

[value1] || [value2] || etc...

Table 2: PHP syntax differences between MySQL and PostgreSQL.

MySQL

PostgreSQL

mysql_query($query,$connection)

pg_query($connection, $query)

mysql_insert_id($queryresult)

pg_result(pg_query("SELECT nextval('mysequence')")); (get the sequence value first, and do your insert using that value)

mysql_fetch_row($queryresult)

pg_fetch_row($queryresult, 0) // (row number can be any positive int)

mysql_result ( resource result, int row [, mixed field])

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pg_fetch_result ( resource result, int row, mixed field) (notice that the field name or index is required)

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1. Spend some time in MySQL, replacing 0000-00-00 dates, etc., with either NULL or some sort of default value. If you have defined unsigned INT columns in MySQL, then check the upper bounds of these columns’ values to be sure they are not too high to fit into a signed INT column in PostgreSQL. Remember, you can always use BIGINT if you need to. 2. Check the column definitions for each table, looking for such things as TIMESTAMP, ENUM, and SET. Devise an appropriate replacement in PostgreSQL. 3. Check the queries in your application for any syntax that will be incompatible with PostgreSQL. 4. If you don’t have a high-performance text editor, get one. You will need an editor that can open very large files and that can select vertical columns. In Windows my favorite is UltraEdit. In Linux/Unix, you could use

Emacs or KATE (KDE Advanced Text Editor). Column mode allows you to easily fix a whole column of data in a MySQL dumpfile. You can select a vertical line and do a search and replace in just the selected column, without disturbing the rest of the text file. You won’t believe how helpful this can be until you use it a few times. In Figure 1 we’ve selected a column with the intention of getting rid of the empty string insert into an auto_increment primary key. This demonstrates another incompatibility: MySQL evaluates an empty string as a DEFAULT value in these cases. To make this work in PostgreSQL, we need to replace that empty string with DEFAULT all the way down, as shown in Figure 2. Of course, this particular operation can be done with a search and replace, or a regular expression, but it’s often easier to use column mode, especially if the column contains many different values.

Figure 1

Figure 2

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5. Test, test, test. Don’t expect to migrate live data without testing. In my experience, it usually took about 2 or 3 test runs to make sure the conversion was correct. All this may seem like a lot of drudgery. Hopefully there will be better tools in the future to perform this migration, but at present it’s the best way to proceed if your data is important to you. In fact, given MySQL’s incompatibility with many SQL standards, you would have the same problem moving to any DBMS. Once you move to PostgreSQL, though, the transition to other database systems should be much easier. And the good part is that when you finish this drudgery you will have an incredible amount of logical power at your fingertips. It’s time to flex your imagination and see just how much you can accomplish with some server-side logic. A whole new dimension of your application has just opened up to you. Plus you will have a much better handle on the actual data that your users have been ‘slipping’ into the database over the life of the system, allowing you to make adjustments as needed. Some PHP developers might be wary of this approach because it looks like we are advocating the reduction of PHP’s responsibility level in an application. There is always a “yes and no” to this sort of thinking. If you can take some load off the shoulders of the PHP side of things, you will have more flexibility and developer time to accomplish other things in PHP. Besides, PostgreSQL

is not limited to one, two, or even three server-side languages for use in functions. At present there are six mature language modules: SQL, PL/PgSQL, Perl, Python, TCL, and C. There are also several more language choices currently in development—one of which is plPHP! That’s right, a procedural plug-in so you can use PHP code inside PostgreSQL functions. Now, tell me which DBMS is PHP’s best friend?

About the Author

?>

Rick Morris' web application projects have included work in CRM, mapping/GIS, content management, and e-commerce. He is also a moderator (as member 'rycamor') of the Database forums at http://forums.devshed.com. Rick lives near Fort Lauderdale, Florida, USA with his wife, daughter, and the world's laziest cat.

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F E A T U R E

by Eric Brown

The calendar module for PHP is a rarely-used group of functions for handling dates in different calendar systems. The calendar module supports the Gregorian, Jewish, Julian, and French Republican calendar systems.

Introduction The basis for converting a date between calendar systems is the Julian Day Count. This integer represents the number of days since January 1, 4713 B.C. int cal_to_jd(int calendar, int month, int day, int year)

The calendar module enables a handful of constants for use in calendar functions. See Figure 1 for supported calendar constants. FIGURE 1: Calendar Constants CAL_GREGORIAN

Gregorian Calendar

CAL_JULIAN

Julian Calendar

CAL_JEWISH

Jewish Calendar

CAL_FRENCH

French Republican Calendar

Most of the world uses the Gregorian calendar. Note that the Julian calendar is different from the Julian Day Count.

Installation To install the calendar module, simply compile PHP with —enable-calendar. The Windows distributions of PHP are complete with the calendar module already compiled in.

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To convert a Julian Day Count to another calendar, use: array cal_from_jd(int jd, int calendar)

The array returned contains information about the requested calendar for the date given. Figure 2 shows an example of the array returned. FIGURE 2: Example output Array ( [date] => 12/12/5763 [month] => 12 [day] => 12 [year] => 5763 [dow] => 0 [abbrevdayname] => Sun [dayname] => Sunday [abbrevmonth] => Av [monthname] => Av )

Combining the cal_to_jd() and cal_from_jd() functions, Listing 1 shows a simple example of converting a Gregorian date to a Hebrew date.

REQUIREMENTS PHP: 4.3.2 (with calendar extension enabled) OS: Any Applications: N/A Code: http://code.phparch.com/16/2 Code Directory: calendar

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Calendar Systems The calendar module supports four calendar systems: Gregorian, Jewish, Julian, and French Republican. The Julian calendar is identical to the Gregorian calendar except leap years occur every centennial instead of every centennial that is not a multiple of 400. The Julian system is no longer in use. The French Republican calendar was created during the French Revolutionary War and was abandoned shortly after. Support for the Julian and French Republican calendars is included primarily for historical purposes. The Hebrew calendar is based upon lunar and solar cycles and is still in use. The Gregorian calendar system is the most widely used calendar system. It is the system that most computers use and the one most computer users will be familiar with. Time and date data types, such as the DATE type used by SQL databases, typically store dates in Gregorian format. Other Useful Calendar Functions To retrieve the number of days in a month of a particular year, the cal_days_in_month() function is used. For example:

and Julian Day Counts to different calendar formats. This bypasses the need for the cal_to_jd() and cal_from_jd() functions in most cases. For example, to convert a Gregorian date into its equivalent Hebrew date, you could use: list($m, $d, $y) = explode('/', date('m/d/Y')); $jd = cal_to_jd (CAL_GREGORIAN , $m, $d, $y); $hebrew = cal_from_jd (CAL_JEWISH , $jd);

The returned array, $hebrew, can be seen in Figure 2. A much easier method to convert a Gregorian date to a Hebrew date is to use the shortcut functions: list($d, $m, $y) = explode ('/', date('d/m/Y' )); $hebrew = JDToJewish (GregorianToJD ($m, $d, $y));

The shortcut functions eliminate the need to memorize the calendar constants and make your code more readable. Another difference between the long functions and the shortcut functions is the returned type. The shortcut functions return the date as one string instead of an array. For example, the long functions LISTING 1: Example converting current Gregorian date to Hebrew

$days = cal_days_in_month (CAL_GREGORIAN , date('m'), date('Y'));

will give the number of days in the current month of the current year in the Gregorian calendar. It also automatically takes into account leap years for you. This is much simpler than traditional methods that attempt to take into account leap years. The cal_days_in_month() function also calculates the number of days for a given calendar. The calendar module includes some utility functions for converting calendar formats to Julian Day Count

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

FIGURE 3: List of date conversion functions string JDtoFrench(int jdcount)

Convert a JD to French Republican

string JDtoGregorian(int jdcount)

Convert a JD to Gregorian (month/day/year)

string JDtoJewish(int jdcount)

Convert a JD to a Jewish date

string JDtoJulian(int jdcount)

Convert a JD to a Julian date

int JDtoUNIX(int jdcount)

Convert a JD to a UNIX time stamp

int FrenchtoJD(int m, int d, int y)

Convert a French Republican date to JD

int GregoriantoJD(int m, int d, int y)

Convert a Gregorian date to JD

int JewishtoJD(int m, int d, int y)

Convert a Jewish date to JD

int JuliantoJD(int m, int d, int y)

Convert a Julian date to JD

int UNIXtoJD(int unix)

Convert a UNIX time stamp to JD

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would return September 1, 2003 as an array of information including separate array keys for the abbreviated and full month name, the date, the year, and full date formats. The shortcut functions would return “9/1/2003” for a Gregorian date and “13/4/5763” for a Jewish date. See Figure 3 for a complete list of these functions. The calender functions can also convert a Julian Day Count to and from a UNIX time stamp. Recall that a UNIX time stamp counts the number of seconds since midnight on January 1, 1970. The conversion functions fail for dates before January 1, 1970 and for dates after October 10, 2037. To convert the current time to a Julian Day Count, use the unixtojd() function. With no arguments, unixtojd() returns the Julian Day Count for the current time and date. Alternatively, a UNIX time stamp can be passed to retrieve the Julian Day Count for other dates. The jdtounix() provides reverse functionality of unixtojd(). The same valid date range applies. To obtain only the month name for a certain date, use the JDMonthName() function. JDMonthName() takes two parameters, the Julian Day Count to use and the mode that you want the month name in. Figure 4 contains a complete list of available modes. For example, using mode 1 on a date of October 1, 2003: $jd = GregoriantoJD (10, 1, 2003); $monthname = JDMonthName ($jd, 1);

Mode 1 generates Gregorian month names such as “January” and “February”. As expected, the above code will give a $monthname of “October”. Mode 0 will generate abbreviated Gregorian names (“Jan,” “Feb,” etc). Mode 4 generates Jewish month names, including Adar II, when appropriate. Practical Use of the Calendar Module To demonstrate a real-world use of the calendar conversion functions, we will set up a dynamic events calendar that displays a Hebrew calendar to those that use it, and a Gregorian calendar to the rest of the world. To mini-

mize date conversion, the dates will be stored as Julian Day counts in the database and the times as offsets in seconds. Events will be entered in either Gregorian or Hebrew format, as appropriate. The full code listing for this example is shown in Listing 2. Please refer to it where appropriate. Information will be stored in a simple text file using comma-separated values. For a more complicated application, a formal database would be appropriate. We will need to store the Julian Day Count, the time offset from midnight in the event’s time zone, the event location, and a short description. A sample entry in the file might look like this: 2452884, 28800, “London, England”, “First Local PHP Meeting, please attend!”

Note the use of the quotations in the string. Since the data may contain commas, the quotation marks identify the strings. The first field of the line is the Julian Day Count for September 1, 2003, or Elul 4 5763. 28800 is the number of seconds for 8:00 am. We will store this as the seconds past midnight GMT. The third and fourth fields are the event location and description, respectively. To read the information from the file, the fgetcsv() function is used. This function reads in a given file resource in CSV format and returns an array of each line. It correctly handles quoted fields, too. Listing 3 shows how fgetcsv() is used in this script. By using a comma-separated file format, the events file can be read into and saved in other programs such as Microsoft Excel and OpenOffice.org Calc. The data can also be imported and exported from most common databases such as MySQL. Organizing the events list into a format easily displayed is more of a challenge. Since numerous events may occur on the same day, an array “tree” can be used efficiently. If two events occur on the same day, they appear under the same index of the array. For example, if two events happen on 2452884 (the Julian Day Count of September 1, 2003), they appear as indexes 0 and 1 under the index 2452884. See the output in Figure 5.

) FIGURE 4: Modes for JDMonthName(int jdCount, int mode) 0

Gregorian (abreviated)

Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec

1

Gregorian

January, February, March, April, May, June, July, August, September, October, November, December

2

Julian (abreviated)

Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec

3

Julian

January, February, March, April, May, June, July, August, September, October, November, December

4

Jewish

Tishri, Heshvan, Kislev, Tevet, Shevat, AdarI, AdarII, Nisan, Iyyar, Sivan, Tammuz, Av, Elul

5

French Republican

Vendemiaire, Brumaire, Frimaire, Nivose, Pluviose, Ventose, Germinal, Floreal, Prairial, Messidor, Thermidor, Fructidor

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LISTING 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77

Listing 2: Continued from page 20 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 1)) 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122

// Is the day a listed event? if(isset($listedevents[$JDmin + $i - 1])) echo “{$i}”; else echo $i; echo “”; // Last day of week needs if(($i - (7 - $firstoffset)) % 7 == 0) echo “\n”; } // Output final empty cells and ending if(($daysmonth - (7 - $firstoffset)) % 7 != 0) { echo str_repeat(“ ”, ($daysmonth - $firstoffset - (7 * (int)(($daysmonth - $firstoffset)/7)) + . ‘’; } // Output details, if any. if(isset($_GET[‘details’])) { echo ‘’; $date = cal_from_jd($_GET[‘details’], $calendar); echo “{$date[‘date’]}
”; // date if(isset($listedevents[$_GET[‘details’]])) { foreach($listedevents[$_GET[‘details’]] as $event) { // Time as 00:00 $time = (int)($event[0]/3600); // Need to round the remaining time after the hour and pad it with a 0 if needed $time .= “:” . str_pad(round(60*(($event[0] % 3600)/3600)), 2, “0”, STR_PAD_LEFT); echo “{$event[1]} {$time}
”; echo $event[2] . “

”; } } else { echo “There are no events on the selected day.”; } echo ‘’; } echo ‘’;

?>

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$JDtoday can now be used to output the month title for the current month using JDMonthName(($JDtoday, mode). Mode is a parameter which determines what calendar the month will be output from. See Figure 4 for a complete list of available modes. For our event calendar, modes 1 (Gregorian) and 4 (Jewish) will be used. echo JDMonthName ($JDtoday, 1);

will output the current month name in the Gregorian calendar. To determine the events for the current month, we can run through the $events array tree. The range for Julian Day Counts for the current month is retrieved via: list($minmonth , $minday , $minyear ) = explode ('/', date('m/1/Y' )); $JDmin = gregoriantojd ($minmonth , $minday , $minyear ); $JDmax = $JDmin + cal_days_in_month (CAL_GREGORIAN , $minmonth , $minyear ) - 1;

$JDmin and $JDmax now contain the range for the current month. The - 1 is required otherwise the range will fall into the next calendar month. Note that the range is inclusive: $JDmin

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Introduction to Bug Management JDDayOfWeek() signifies the return type of the offset of the first day of the month, which will return an integer 0 through 6 for Sunday through Saturday. The rest of the calendar is output through a simple loop that outputs a starting table row at the beginning of the week, seven cells containing the date, and the ending table row:

“Organizing the events list into a format easily displayed is more of a challenge.”

if(isset( $_GET['details' ])) { echo '' ; $date = cal_from_jd ($_GET ['details' ], $calendar ); echo " {$date['date']}
" ; if(isset( $listedevents [$_GET['details' ]])) { foreach( $listedevents [$_GET['details' ]] as $event) { // Time as 00:00 $time = (int)( $event [0]/3600); // Need to round the remaining time after // the hour and pad it with a 0 if needed $time .= ":" . str_pad (round(60*(($event [0] % 3600)/3600)), 2, "0", STR_PAD_LEFT ); echo "{$event [1]} {$time }
"; echo $event [2] . "

" ; } } else { echo "There are no events on the selected day." ; } echo '' ; }

$daysmonth = $JDmax - $JDmin + 1; for($i = 1; $i

Eric Brown is a software engineering student at the Milwaukee School of Engineering in Milwaukee, Wisconsin USA. He can be reached at [email protected].

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23

Using the GD library with PHP

F E A T U R E

by Pavel Koutny

Introduction About a year ago I worked on an accounting solution for a local ISP. I needed, for the first time, dynamically generated charts. The charts showed statistical information across time; things like bit-rate, etc. I happened to have GD installed on my development machine, so I tried it out. The results were great! What is GD? GD is an open source graphics library from Thomas Boutell. Its primary goal is to create pictures for the web. The GD library enables the developer to create and manipulate many different image formats, including JPEG, PNG and WBMP. With ease, you may use GD for creating images, as well as drawing, rotating, cropping, resizing, and re-sampling them. If you want to create images in GIF format, that will be a problem. The Unisys LZW compression algorithm patent has expired in the United States, but until that patent expires everywhere else next year, the GIF functions stay removed. If you absolutely must work with GIF images you can revert to an earlier version (

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Introduction to Statistical Charting using PHP

JPGraph PHP provides an interface to the GD functions to handle programmatic creation of several image formats. This can be used to graph statistical functions and provides, at the expense of laborious coding, the finest level of control. A more efficient alternative is to use JPGraph, an object oriented library for creating professional graphs within PHP. JPGraph utilizes the GD functions and FreeType library to handle true type fonts. JPGraph can be downloaded from its homepage at: http://www.aditus.nu/jpgraph/

Your PHP installation must, therefore, have GD and TTF support compiled in before using JPGraph. Details of achieving this are outside the scope of this article, but I successfully used the following configure options on my system: ./configure —with-mysql —with-gd —enable-gd-nativettf —with-ttf

JPGraph is written entirely in PHP and takes a truly object oriented approach to the creation of graphs. Each graph image is created by a graph object, with xaxis and y-axis objects as properties. Each plot— such as a line, pie or bar plot—within a graph is created by a plot object which is added to the graph object. The library is called by simply including jpgraph.php from the JPGraph distribution source directory and instantiating a Graph object. The Graph constructor accepts image dimensions, and properties such as

BackgroundImage, Scale and Legend can be set on the Graph. For each type of plot being used, include jpgraph_plot-type.php; for example, to create a line plot include jpgraph_line.php and instantiate a LinePlot object. NOTE: There are 2 lines of code used to include the JPGraph libraries in the PHP code—be sure to adjust their path designations to the directory where jpgraph is located (installed) on your computer. An example of the designation on a Linux machine include(‘/usr/phpinc/jpgraph.php’); include(‘/usr/phpinc/jpgraph_scatter.php’);

Could be designated as the following on a Windows machine include(‘C:/setups/JPGraph/jpgraph-1.13/src/jpgraph.php’); include(‘C:/setups/JPGraph/jpgraph-1.13/src/jpgraph_scatter.php’);

JPGraph is perfect for our purposes of plotting statistical values graphically. The first plot we will produce is a frequency distribution graph. Plotting Distribution The manner in which values are distributed throughout a data set is best illustrated using a frequency distribution graph. This is a histogram with an X axis of each value within the range and a Y axis of frequency of occurrences within the set. JPGraph accepts the data for each axis as a one dimensional array of values. This fits with the object model created earlier in this article to represent sales Listing 5: stddevcalc.php

Listing 4: meanmediancalc.php 1

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data. The data set needs only to be iterated through to create an array of value frequency for the Y axis and value range for the X axis. It is not required to specify the data for the X axis; JPGraph will automatically determine the range of values from the Y axis data. If, however, the programmer desires to set the numeric range and intervals for the axis it can be specified. For the following example we will not specify explicit values for the X axis. The class definitions in Listing 2 (ssalesclasses.php), the database interaction code in Listing 3 (ddataprep.php), and the descriptive statistical calculation functions in Listing 4 (mmeanmediancalc.php) and Listing 5 (sstddev.php) have all been combined in statsinc.php to provide one library for our graph creation code. Previously we have used the sales value variable of the data set, but for the purpose of frequency distribution this is not suitable. Since the sales value is the product of unit quantity and unit value, there will be a wide range of unique sales values. The sales quantity is more appropriate, as these values will be far more constrained. The code in Listing 6 (ffreqdist.php) uses this library and the aforementioned iteration technique Listing 6: frequdist.php 1

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to create JPGraph histograms of frequency distribution for unit quantity per sale. This code produces the following PNG image:

From this we can see that sales quantities are mostly in the range 1-10, with 1 unit being the most frequent value with 7 occurrences. Overlaying Descriptive Statistics To further illustrate the nature of value distribution throughout the set, the mean, median and standard deviations can be calculated from the data set and these descriptive values overlaid on the frequency distribution graph. JPGraph provides the Set() method in both the title and subtitle objects within each graph object, which can be used to print this kind of information within the graph image rather than as subscript text. The array used to populate the Y-axis of the graph ($$yaxisdata) is indexed by quantity, with the indexed values being the number of occurences of that quantity. To calculate the mean, median and standard deviation, we need a second, sequentially-indexed array of all the sale quantities ($$statsdata). For the mean function to work—returning the value at the mid-point of the array—the array must be sorted incrementally. The code in Listing 7 (ffreqdistoverlay.php) extends Listing 6 (ffreqdist.php) to perform this. This code produces the following PNG image:

A mean slightly higher than the median indicates that there are a few very high values in the set skewing the mean.

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Listing 7: freqdistoverlay.php 1

Listing 8: correlation.php 1

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Correlation The term correlation refers to the extent to which the value of one variable within a data set is indicative of another. For example, there would undoubtedly be some level of correlation between sale quantity and sale value. Correlation is calculated using the Pearson coefficient of correlation equation. This equation is defined as follows: R=sum((X-mean(X))*(Y-mean(Y))/(N*stddev(X)*stddev(Y)) R X Y N

is is is is

Pearson coefficient of correlation each value of the first variable each value of the second variable the number of pairs of variables

The result returned will be a signed value between -1 and 1. A value of 0 indicates there is no correlation at all, while a value of -1 or 1 indicates that X predicts for Y perfectly. The sign of the result (positive or negative) indicates whether the correlation is positive or negative. A positive correlation means a higher value of X indicates a higher value of Y while a negative correlation means a higher value of X indicates a lower value of Y. Since we already have functions to calculate the mean and standard deviation, this algorithm can be implemented as an extension to the existing code in statsinc.php. Listing 8 (ccorrelation.php) implements the algorithm and has been included in statsinc.php for future code snippets. This algorithm can then be implemented to determine the correlation between each pair of variables in the data set. To achieve this, we must iterate through the sales data objects and form a pair of arrays for each pair of variables we wish to examine. Each pair of arrays must then be run through the correlation() function provided in statsinc.php. The code in Listing 9 (ccorrelall.php) determines the correlation between each element of salesman data and their associated sales value, Listing 9: correlall.php 1

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FEATURES


and prints the results. This calculation will help us understand which factors influence salesman performance. This code produces the following output: Years Experience correlates to Sale Value: -0.25942226790464 Education correlates to Sale Value: 0.1235363100083

This indicates that X, or Sale Value, is likely to indicate Listing 10: regression.php 1

Listing 11: linebestfit.php 1

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a slightly lower number of years experience. Perhaps the older salesmen have lost their fizz? It also indicates that Sale Value is likely to indicate a very slightly higher level of education. Perhaps the better educated salesmen are more skilled? Calculating Simple Regression We now know that the salesmen who have a little less experience but a little more education are most likely to deliver strong sales results. This knowledge can be applied to predict the sales value a candidate salesman will achieve based on the values of his years experience and level of education. The correlation coefficients previously calculated indicate the degree to which these factors predict sales value. When run through a technique called Simple Regression, the correlation coefficients can be used to predict the most statistically likely sales value any given candidate will achieve. Simple regression only allows for one X variable to predict the value of Y. A more complicated technique called Multiple Regression can cope with multiple X variables, but this is beyond the scope of this article. Because the negative correlation of Years Experience to Sale Value is stronger than the positive correlation of Education to Sale Value, we will use Years Experience as the X value and Sale Value as the Y value. Listing 12: scatterplot.php 1

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Simple Regression is calculated using the Regression Equation for Predicting Y from X: Yp = R*(stddev(Y)/stddev(X))*Xp R(stddev(Y)/stddev(X)*mean(X)+mean(Y) Yp is the predicted score of Yp Xp is the potential X value being used to predict Yp R is the coefficient of correlation between X and Y X is each value of X Y is each value of Y

This algorithm can be implemented in PHP by further building on our existing mean, standard deviation and correlation calculation functions. Since the stddev() and mean() functions perform their own required iteration internally, the function to calculate regression will not require iteration. The code in Listing 10 (rregression.php) implements the algorithm and prints the results for a salesman with 1 year experience. This function has been included in statsinc.php for all further code snippets. This code produces the following output: A salesman with 1 year exp will most likely sell: $7150.07 of product

Plotting a Line of Best Fit If we were to use the regression equation and plot every potential value of X against the predicted value of Y, a straight line would emerge. This line, called the line of best fit, is useful for providing a quick graphical reference for determining any the predicted Y value for any given X values. We can plot a line of best fit by simply calculating Y using the regression algorithm for the lowest and highest values of X on the plot and drawing a straight line between them. JPGraph’s LinePlot object is perfect for this purpose. JPGraph, however, only draws X axis ‘ticks’ for elements included in the plot. With this in mind, in order to produce a more readable plot, the code in Listing 11 (llinebestfit.php) iteratively calculates Y for X of 0 to 5 and plots a line of best fit between the points using JPGraph. This code produces the following PNG image:

ment is overlaid on the line of best fit. The code in Listing 12 (sscatterplot.php) performs this by building a JPGraph scatterplot object from the same $datax and $datay arrays constructed in Listing 11 and adding it to a graph object . This code produces the following PNG image:

Part 3 – Conclusion The statistical functions which this article has outlined have a myriad of applications, limited only by the imagination of the programmer. Sales data was used as a classic example, but any numeric data can be dealt with in the same manner. Descriptive statistics are best applied in applications designed to present large amounts of data for rapid comprehension by the user. As the example of overlaying mean, median and standard deviation values over a frequency distribution graph showed, when descriptive statistics are combined with a graphical representation of the data set, a powerful data analysis tool is formed. Inferential statistics are best applied when you wish to infer conclusions or predict future sequences of data. Various advanced techniques such as Multiple Regression Analysis and Linear Analysis extend upon the functionality of Simple Regression as described above. As the example of predicting a salesman’s performance showed, this can be a powerful tool for prediction and forecasting.

About the Author

?>

David works as a document imaging and OCR programmer for a small Australian company. He spends his spare time writing PHP code and studying environmental science.

The way in which this represents the nature of the existing data can be best seen when a scatter plot of the years experience and sales value values for each ele-

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Tips & Tricks By John W. Holmes

More Secure PHP Coding In last month’s issue, David Jorm and Jody Melbourne wrote a great article on securing your PHP code. One additional point that I wanted to discuss that goes along with this idea is taking care of single and double quotes in your user-supplied data. We learned in David and Jody’s article that you need to escape quotes in text from users in order to prevent SQL injection attacks, for example. The area I want to focus on is handling those quotes correctly when it comes time to display that data within an HTML form element like a text input or text area. The “problem” with HTML (for this discussion) is that there is no escape character. In PHP, you could create a string such as the following.

the string for the input element. This means the actual value of the input element will appear as “My name is \” (without the quotes), leaving the rest of our string as an unrecognized attribute to the input element. HTML is forgiving in that it just ignores the “unknown attribute”, though. So why is this a big deal? Besides the obvious problem of losing part of your text, you’re also opening your application up to a cross-site scripting vulnerability. A malicious user can insert a double quote to end your value attribute and then add a few extra JavaScript commands to cause some trouble. Normally the value portion of an input element is coming from a PHP variable. So we need to find a way from within PHP to encode the quotes within that text. The solution is to turn it into an HTML entity, and the functions that will do that for us are htmlentities() and htmlspecialchars(). These functions will take single and double quotes and convert them into their HTML entities, ' and " respectively. Running htmlentities() on the above string and

“HTML does not understand the backslash as an escape character and displays it literally.”

$str = “My name is \”John\”, okay?”;

The backslash characters tell PHP to insert a literal double quote in the string. If you try to do the same with HTML when inserting text into an input element, it will not work.

HTML does not understand the backslash as an escape character and displays it literally. The double quote after the first backslash is then seen as the end of October 2003

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REQUIREMENTS Code: http://code.phparch.com/16/7 Code Directory: tricks

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TIPS & TRICKS placing it into the value portion of the input element will now end up as this:

While that looks weird when viewed as the HTML source, trust me when I say that it will appear in the browser window as an input text box with double Listing 1 1

quotes around the name John. The htmlentities() and htmlspecialchars() functions will convert only double quotes by default, though. As a second parameter, you can pass one of three constants to tell the functions how to handle quotes. The options are to convert double quotes only, convert double and single quotes, and to not convert any quotes. Text areas in your form are vulnerable to the same type of problem. The user’s text may contain a string and the remainder of the data will be shown as HTML. If you followed the original article and are taking care of < and > characters by converting them to the < and > HTML entities, then it will prevent any vulnerabilities. The functions htmlentities() and htmlspecialchars() will do this conversion for you, though, while also taking care of double quotes, so you sort of kill two birds with one stone.

Listing 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

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TIPS & TRICKS The only question that remains is when to do this conversion. You obviously want to do it at some point before you have to show this data in a text box. The ideal time to do it, though, depends upon your application. If you have data that is mostly displayed and edited over the web, then it would be efficient to do this conversion once when the data is accepted instead of every time it’s displayed or edited. If your data is frequently used in other formats than HTML, such as PDF files, email text, etc, then you would more than likely want to store the data as regular text and do the conversion only when being viewed or edited over HTML (unless you were sending HTML emails for some odd, odd reason). Either way, if you are using PHP 4.3.0 or newer, you also have the html_entity_decode() function that will perform the opposite of htmlentities() and htmlspecialchars().

Listing 3 1

html_most_entities() The question was raised earlier this month on the PHP mailing list about how to do a htmlentities-like conversion on a string, but leave the < and > characters unchanged. A simple way to do this would be to use the get_html_translation_table() function to get an array filled with the conversions that htmlentities() will perform. You can then unset() the elements you do not want converted, and then use strtr() to perform the remaining conversions. An example of how to do this conversion is shown in Listing 1, and ignores the < and > characters. It could easily be adapted to exclude any of the other characters, or to perform additional conversions. For example, if you have a “bad word” array for your site that you normally perform string replaces for, you could add that array to the array returned from get_html_translation_table() and do the conversions all at once. This is also shown in Listing 1. The output is shown below. It's a string with "*******" & the ä character &

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XHTML Compliant Source Code Jeremy Harnois of jharnois.com offers up the two functions shown in Listing 2 and 3, show_source_php2xhtml() and

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TIPS & TRICKS show_source_css2xhtml() as ways of showing syntax-highlighted PHP and CSS source code that is XHTML compliant. The first works by taking the output of the PHP function show_source() and replacing the deprecated tags with <span> tags and CSS classes. The CSS source function uses Perl-compatible regular expression functions to match the bits of CSS code that need to be wrapped in a certain <span> and CSS class. In order for these functions to work, you must, as explained in the comments, create a CSS file that defines the color, font, etc, you want applied to each of the code parts. You must define CSS for bg, comment, default, html, keyword, and string. For example, if you want green strings in your PHP source code, defining some CSS such as

CSS. You can do the same for the rest of the values, or write your own CSS. Send in Your Tips You can get published like Jeremy in the online and print edition of php|architect by sending in your useful and/or time-saving tips for working with any aspect of PHP. Submit your tips and general comments and suggestions to [email protected] for consideration for the next issue. Contributors who’s tips are published will receive a free online version of php|architect.

span.string {color: #0000FF}

will achieve those results. Since the default colors used by show_source() are defined in the php.ini file, you could also use ini_get() to pull those values out and create your CSS. A line such as span.string { color: ;

About the Author

?>

John Holmes is a Captain in the U.S. Army and a freelance PHP and MySQL programmer. He has been programming in PHP for over 4 years and loves every minute of it. He is currently serving at Ft. Gordon, Georgia as a Company Commander with his wife and two sons.

will pull the value from php.ini and assign it to your

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Bits & Pieces Real. Interesting. Stuff.

More Regular Expressions Last month I mentioned a couple of tools* for understanding and planning regular expressions. Only days after I wrote this, the PHPEdit Network (creators and maintainers of the very capable PHPEdit IDE) announced the release of their RegExpEditor. This tool, available at: http://www.phpedit.net/products/RegExpEditor RegExpEditor is like a lite version of the Regex Coach (from last month), but has the advantage of being developed by members of the PHP community, and actually wraps the preg_XXX functions themselves (see Figure 1).

every line of code, and start enjoying the magazine. It did, however, seem odd for so many mistakes to occur in so few lines of code (especially in this Article). —Jesse We usually check every code snippet that we publish by running it through our PHP interpreter. The problem with this particular article is that it contained many small code listings that were difficult to test, and their purpose was more for illustration purposes than for actual execution. However, that’s not an excuse for publishing incorrect code, and that’s definitely something we should have caught. —Marco

B I T S

Client-Side PHP? A recent Mozilla project may cause some controversy. In July Dr. Thomas Schilz started MozPHP, a Mozilla-PHP integration package. There is currently little documentation or direction at the project websites (http://www.thomasschilz.de/MozPHP/ and http://mozphp.mozdev.org/), but this project promises to (once again) help take PHP to new frontiers. Although, I suppose these are not entirely new frontiers, since I remember an announcement last year from Wez Furlong about an implementation of client-side PHP in Internet Explorer

First of all, I love the magazine, and I enjoy every issue. But I would like to ask that you stop promoting as many commercial software products, especially when there are so many worthy free software projects out there. How many free software projects had releases in the last month? Yet you chose to focus on a $400 SDK in your New Stuff column. Don’t get me wrong: we need commercial software in the PHP world for the language to be considered viable. But to me, these articles do not promote learning about PHP, and only serve the company selling the product. —Eric

http://www.zend.com/lists/php-dev/200205/msg00634.html

It will be interesting to see how MozPHP fares.

Letters First of all, I’d like to state how much I enjoyed the content of this magazine. Not only did I find the articles to be novel and applicable, they ‘tickled my fancy’ for areas I have yet to delve into. Also the tips and tricks alone seem to be worth the price of the magazine :) However, I would like to raise a concern. While reading the first article, I was unpleasantly surprised to come across ‘so many’ code errors. I eventually decided to stop analyzing

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The PHP Community is extremely vibrant, as demonstrated by the many projects in existence (as you justly noted), which we usually cover either in the What’s New section of php|a, or, as we have done in the past, in the product reviews themselves. PHP is also witnessing the blossoming of a lively commercial community. This is an important step toward its acceptance in the marketplace, and we feel that our role is, at least in part, to try and foster this community as well. We try our best to keep a balance between the two worlds, and to remain as objective as possible. At the same time, I think our commitment to the open-source world has been quite good—to this date, we are only one of a handful of magazines dedicated exclusively to PHP, and the only one to

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BITS & PIECES actively support its community in a tangible way through our Grant Program, which provides financial assistance to opensource PHP projects. —Marco

php|architect Article Code Formatting There was recently a discussion in the php|a forums about the varying code styles across articles. boots started off: “It is a trifle in many respects, but I can’t help but notice that code formatting rules are anything but consistent across articles. I feel that php|a has the opportunity to be an exemplar in this regard—particularly since an article was already dedicated to this topic.” To this, our benevolent dicta—er—publisher (Marco) remarked that we do this consciously to allow the author to express herself freely, and to allow the magazine to offer exposure to different styles and ideas. Another forum member, Karin, agreed. “I think it’s great to see different code formatting styles by the authors of the articles. I love to see different styles and deciding for myself what I find most efficient/useful/... of each style. Sure it would probably be better if all (professional) php programmers used the same style and naming conventions etcetera, but it’s also known that different groups/programmers don’t agree which is best, so I think it’s good to see those different styles in action.” In a later post, Marco followed up with the following note about the separation of content and code formatting:

“Code formatting is directly related to the subject matter of our magazine. There are no hard-and-fast rules (besides the fact that the code has to fit in the magazine itself), and code formatting is not a mere matter of aesthetics, but one with very practical implications. As editors, we think of ourselves more as “content brokers” than filters. We try to bring you articles that are compelling, interesting, well-written and accurate, but other than that we try our best not to force any particular precept on our readers, so that they can fully appreciate the variety of possibilities out there. It’s a tricky job, and I’m sure we falter here and there, but I think that’s the right way to go, particularly considering that code formatting is one area where not only there is no accepted standard (sorry, the PEAR standards are good for PEAR but they are not widely accepted).”

boots later offered an interesting idea that instead of allowing all different styles across all articles in an issue, we could use a code formatter and offer a different style each month. The topic of coding style ranks up there with other religious debates such as Vi vs. Emacs, and everybody has a different opinion. For now, at least, we choose to stay out of it, and allow (mostly) free expression in this regard.

Has anything been eating at you? Do you have a bone to pick on this particular topic, or anything else we’re doing? We’d love to hear about it! Send us a note at [email protected], or drop us a line in the forums.

Figure 1

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Digital Monopoly

e x i t ( 0 ) ;

By Marco Tabini

I

’m fairly convinced that 2003 will become known as the year in which intellectual property rights stole the spotlight. Over the last few months, the Linux community has become embroiled in a bitter battle against SCO over who really owns some of the code that is present in the open-source operating system. At the same time, the Recording Industry Association of America (RIAA) has begun suing computer users who are caught swapping files on peer-to-peer networks over the Internet. Call me crazy—everybody around here does—but I happen to think that these are both very good things. Based on what I have been able to see, there is no doubt in my mind that SCO’s claims are nothing but a desperate attempt by a desperate company to make one last effort at surviving. Their actions, however, have had the conse-

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quence of causing just about everyone to take a good hard look at intellectual property rights, their meaning, and their implications for the open-source community. Since the whole SCO fiasco started, I suspect that many people have—for the first time—been reading, questioning, and trying to understand the GPL. Some people may have even begun to finally understand the differences between “free”, as in speech, and “free”, as in beer. At the opposite end of the spectrum, we have the RIAA going after individual users for their alleged illegal copying and sharing. Why is this a good thing? To answer this question, one must understand what file copying really means. Since much of the business of my company is based on the concept of intellectual property, I happen to agree with the RIAA that copying anything—be it

music, software, books or magazines—without the permission of the copyright owners is illegal, period. There is no “but”, no “maybe”, no “he’s just a kid”. Would you condone your kid dropping into a store and shoplifting? I certainly hope not. However, at a deeper level, copying is a form of expression. It is a fundamental tenet of the free market that the market must be able to regulate itself through simple rules of supply and demand. Customers must have a way to signal to the suppliers their willingness (or lack thereof) to purchase their goods in one way or another. If demand dwindles, the supply generally becomes more accessible (e.g., the price goes down). Conversely, if demand increases, the price goes up. This theory is usually referred to as the “invisible hand”, and it’s easy enough to see that on a very large 72

scale it works, although it can be manipulated in other ways (the airline industry has been trying to do so for years— which accounts for the fact that the person sitting next to you on your $1,000 flight only paid $200). As far as intellectual property is concerned, copying is, on a large enough scale, nothing more than an expression from the demand side of the equation that the supply is acting with iniquity towards the market. If you think I should have myself checked out at a psychiatric hospital, consider this: duplicating a DVD on a large scale costs about $.25-$.50. Duplicating a VHS tape can run much higher, sometimes even $1. Yet, a DVD costs on average between $20-$30, while a VHS type hardly ever gets to $20 any more. In addition, DVD’s are much lighter than tapes, resulting in lower shipping and handling cost. Why, then, are we paying more for the DVD? The same concept applies to CD’s and cassette tapes. Whatever the recording industry’s motivation for these price differences, they obviously do not sit well with the public, who copy their products illegally rather than not buying because it’s simply easier to do so. Of course, there are some people that would copy intellectual property even if it were free—but those are, in my experience, the minority. Given a fair October 2003

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opportunity to be honest, most people will choose to do so, resorting to illegal activity only when they feel they’re been played for fools by the “system”—whatever that means. Over the last few years, some US laws have gone a long way in impeding the free market’s needs to express itself and flow smoothly. The Digital Millennium Copyright Act creates a digital monopoly that grants the copyright holders an unfair advantage by depriving the demand of its fundamental way of expressing its power in the free market. This simply makes it possible for the quality of the products sold to drop dramatically (Britney Spears anyone?) while the price remains the same or increases. Thus, a fundamental check in the system has been removed—the supply is now free to be lazy and drop innovation down the tubes because it no longer fears the demand—but I digress. How can these lawsuits brought forward by the RIAA, or SCO’s outrageous claims, be good for the public? Simple—the culprits are shooting themselves in the foot. An unfair advantage that can easily be taken away must be used carefully, and the RIAA, for one, has chosen a very bad time—election time in the US, to be precise—to take advantage of this. As I write my column this month, a lady who lives in a

New York housing project has settled a lawsuit from the RIAA for $2,000 because her 12-year-old was file swapping. That’s a great strategic step for the recording industry—go after the socially disadvantaged because they don’t buy your grossly-overpriced products. Make no mistake about it— this behaviour is not going unnoticed. Politicians—ever the bloodhounds—are taking notice and won’t sit idly by while their votes are taken away by a greedy bunch of Hollywood types. This inescapable fact must be pretty obvious to the recording industry itself: SCO has just published an “open letter” to the open-source community. That it is fraught with obviously distorted facts only reinforces my view that SCO is finally feeling that the situation is getting out of hand. By the same token, Universal has lowered the wholesale cost of its CD’s, in the hopes of wooing more customers away from file sharing. However, one hand offering an olive branch while the other is bitch-slapping doesn’t do much good to your cause, and just makes you look weaker to the less-than-casual observer.

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php|architect (October 2003)

Scientific american (October 2003)

October

October)

October)

Active Mining: Second International Workshop, AM 2003, Maebashi, Japan, October 28, 2003, Revised Selected Papers

Information and Communications Security: 5th International Conference, ICICS 2003, Huhehaote, China, October 10-13, 2003, Proceedings

Digital Watermarking: Second International Workshop, IWDW 2003, Seoul, Korea, October 20-22, 2003, Revised Papers

2003)

2003)

Embedded Software: Third International Conference, EMSOFT 2003, Philadelphia, PA, USA, October 13-15, 2003, Proceedings

High Performance Computing: 5th International Symposium, ISHPC 2003, Tokyo-Odaiba, Japan, October 20-22, 2003, Proceedings

Inductive Logic Programming: 13th International Conference, ILP 2003, Szeged, Hungary, September 29 - October 1, 2003, Proceedings

Distributed Computing: 17th International Conference, DISC 2003, Sorrento, Italy, October 1-3, 2003, Proceedings

Information Security: 6th International Conference, ISC 2003, Bristol, UK, October 1-3, 2003, Proceedings

2003)

2003)

2003)

2003)

October Skies

October Men

October Song

October 1988)

October revolution

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php|architect (October 2003)

Scientific american (October 2003)

October

October)

October)

Active Mining: Second International Workshop, AM 2003, Maebashi, Japan, October 28, 2003, Revised Selected Papers

Information and Communications Security: 5th International Conference, ICICS 2003, Huhehaote, China, October 10-13, 2003, Proceedings

Digital Watermarking: Second International Workshop, IWDW 2003, Seoul, Korea, October 20-22, 2003, Revised Papers

2003)

2003)

Embedded Software: Third International Conference, EMSOFT 2003, Philadelphia, PA, USA, October 13-15, 2003, Proceedings

High Performance Computing: 5th International Symposium, ISHPC 2003, Tokyo-Odaiba, Japan, October 20-22, 2003, Proceedings

Inductive Logic Programming: 13th International Conference, ILP 2003, Szeged, Hungary, September 29 - October 1, 2003, Proceedings

Distributed Computing: 17th International Conference, DISC 2003, Sorrento, Italy, October 1-3, 2003, Proceedings

Information Security: 6th International Conference, ISC 2003, Bristol, UK, October 1-3, 2003, Proceedings

2003)

2003)

2003)

2003)

October Skies

October Men

October Song

October 1988)

October revolution

Miss October

October Girls

October Girls

October Skies

October Skies

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