Object-oriented programming (OOP) was integrated into the PHP version 3 in 1998, including basic class and object support. In 2000, PHP4 added some functionality, but suffered from its non-intuitive handling of references with objects handled like value types.
Finally, in 2004, PHP5 included an extensive rewrite of object handling with the introduction of Zend Engine 2, featuring a comprehensive feature set and increased performance.
But at that time, the PHP object model was far too brief. We could really talk about object oriented programming. PHP Developers are then examined the issue and improved the object model that, since version 5, has nothing to envy to other objects languages like Java or C++.