On the positive side, this edition of PHP does bring improved performance and a new suite of MySQL functions. Backward incompatibility is limited to a list of ten issues that can be found at: http://www.php.net/manual/en/migration5.incompatible.php. Minimally, there are only minor configuration file changes that need to be made to the web server. These changes are found at: http://www.php.net/manual/en/migration5.configuration.php. Several directives have been introduced for configuring php.ini files mainly dealing with hashes for encryption. Read about them at http://www.php.net/manual/en/migration5.newconf.php.

Some very useful functions have been added to PHP5. It’s been nine years in the making, but PHP5 now includes two functions to uuencode and uudecode. Combining those functions with the new socket and stream functions, developers can create a lots of "kewl" applications. An application to automatically encode and decode files to and from news servers comes to mind as an example of how to incorporate these new functions. At that point of course, a developer could use any of PHP’s existing functions to continue to manipulate the files, store the contents in databases, and so on. Read about those and all the other new functions at: http://www.php.net/manual/en/migration5.functions.php.

An addition to error reporting aids developers in keeping their code up-to-date. The E_STRICT message tells developers when their code is using deprecated functions or is in danger of not being forward compatible. However, don’t assume that E_STRICT will be output if using E_ALL, because it won’t. E_STRICT must be explicitly declared to output its suggestions to PHP 5 code.

While the rewriting of PHP’s object model to essentially that of the Java object model does raise flags about the direction of PHP, it is still a powerful addition to the PHP5 release. Java became successful for a reason. It’s intelligently designed and facilitates code reuse. By borrowing the best features of Java’s object model, PHP has leveraged itself with far more credibility as a programming language that can stand on its own two feet (even if Sun, Borland and Macromedia are holding it by its arms).

Some vital re-workings in the PHP object model lie in how objects are treated in low-level fashion. Instead of passing the actual object itself, PHP’s object model passes by reference. Now when operating on objects, developers can pass around multiple handles to the actual object allowing for more powerful and efficient applications. Existing PHP objects do not need to be re-written to take advantage of this change in PHP 5.

In general, developer’s who have experience with Java will easily adapt to PHP 5’s object model. On the downside, if PHP is a developer’s primary language and he or she hasn’t been introduced to the world of static variables, public and private methods and the host of aspects included with this new model, they may have a bit of a learning curve adopting the higher-level format of object-oriented programming in this release. Overall, though, this change will be a plus for creating large-scale, object-oriented applications with PHP.