PHP 5 Power Programming

Only time will tell if the PHP 5 release will be as successful as its two predecessors (PHP 3 and PHP 4). The new features and changes aim to rid PHP of any weaknesses it may have had and make sure that it stays in the lead as the world’s best web-scripting language.

This book details PHP 5 and its new features. However, if you are familiar with PHP 4 and are eager to know what is new in PHP 5, this chapter is for you.

When you finish reading this chapter, you will have learned

• The new language features
• News concerning PHP extensions
• Other noteworthy changes to PHP’s latest version

New Object-Oriented Model

When Zeev Suraski added the object-oriented syntax back in the days of PHP 3, it was added as “syntactic sugar for accessing collections.” The OO model also had support for inheritance and allowed a class (and object) to aggregate both methods and properties, but not much more. When Zeev and Andi Gutmans rewrote the scripting engine for PHP 4, it was a completely new engine; it ran much faster, was more stable, and boasted more features. However, the OO model first introduced in PHP 3 was barely touched.

Although the object model had serious limitations, it was used extensively around the world, often in large PHP applications. This impressive use of the OOP paradigm with PHP 4, despite its weaknesses, led to it being the main focus for the PHP 5 release.

So, what were some of the limitations in PHP 3 and 4? The biggest limitation (which led to further limitations) was the fact that the copy semantics of objects were the same as for native types. So, how did this actually affect the PHP developer? When assigning a variable (that points to an object) to another variable, a copy of the object would be created. Not only did this impact performance, but it also usually led to obscure behavior and bugs in PHP 4 applications because many developers thought that both variables would point at the same object, which was not the case. The variables were instead pointing at separate copies of the same object. Changing one would not change the other.