PHP is an open source web development, server-side scripting language that drives thousands of web applications today, such as Wordpress, Facebook, Wikipedia, Drupal and Digg. PHP allow you to create dynamic web pages and integrates directly into HTML webpages. This general purpose scripting language has somewhat humble beginnings, but has since grown to be a web development standard.
PHP/FI
PHP is the evolution of a set of Perl scripts created by Rasmus Lerdorf in 1995 called PHP/FI. Originally, PHP stood for Personal Home Page Tools. Lerdorf used PHP/FI to track pageviews on his online resume. As his needs grew, he developed PHP to include more functionality—namely the ability to access databases and produce dynamic websites specific to the user. He did so by implementing a larger C implementation, and amended PHP to PHP/FI, which stood for Personal Home Page / Forms Interpreter. He released the source code of PHP/FI to the public in order to elicit comments, bug fixes and other improvements. At this phase, PHP/FI resembled Perl.
When PHP/FI 2.0 was released, it began taking on the resemblance of what we know of today as PHP. PHP/FI 2.0 was released in 1997 and quickly gained a cult following and was installed on about 50,000 domains.
PHP 3
PHP 3 was the next major stepping stone the on the way to the PHP of today. PHP 3 included a major overhaul of PHP/FI with a focus on extensibility. PHP/FI 2.0, which was too underpowered for applications such as eCommerce storefronts, was mostly halted while Lerdorf teamed up with Zeev Suraski and Andi Gutmans to rewrite PHP 3. In addition to the collaboration from these two main developers, the wider community was invited to add extension modules to the pre-existing protocols, APIs, databases and infrastructure. PHP 3.0 also adopted an object oriented syntax. PHP 3.0 was officially released in June 1998 after about 9 months of public beta testing. PHP dropped its “personal” moniker and is now known as PHP Hypertext Processor, a recursive acronym that is a common joke among developers.
PHP 4
PHP was rewritten again by Andi Gutmans and Zeev Suraski to improve its performance and allow it to run more complex web applications. This would improve PHP’s modularity and allow greater use of third-party APIs. The new engine was called the “Zend Engine,” which is a combination of Gutman’s and Suraski’s first names. The Zend Engine supports more web servers, HTTP sessions, output buffering and greater security for users.
PHP 4.0 was officially released in May 2000 and is used by over 20 percent of the domains on the Internet.
PHP 5
The latest iteration of PHP is PHP 5, which is based on another update of the Zend Engine. Using Zend Engine 2.0, PHP 5 has a new object model and enhanced functionality for XML and SQL, among other new features. As of April 2007, over 20 million Internet domains use PHP.