Why is it necessary to drop support for PHP 4?

PHP version 5 adds a number of new features and design changes that make developing robust, secure, feature-rich software faster and easier. Those features do not exist in older versions of PHP 4, however, and many are very hard to emulate. Such features include fast and easy XML support for improved web services, better timezone handling, vastly improved database tools and input tools to make PHP applications more secure, and many others.

Projects that support PHP 4 cannot make use of those newer features, however. That means projects have to choose between supporting PHP 4, which has been in maintenance-only mode for over three years, or enabling modern web applications and services. For a long time many projects have chosen to support PHP 4 because of the large number of web hosts running PHP 4. Unfortunately that has resulted in a "chicken and egg" problem where web hosts have no incentive to upgrade to PHP 5, which means PHP developers can't use PHP 5's new functionality even if they want to.

By announcing that many leading open source projects will drop legacy support for PHP 4 at a fixed later date, we believe we can break that cycle and encourage web hosts to upgrade and allow open source developers to build faster, more secure, more powerful web applications.