The original PHP release was created by Rasmus Lerdorf in June 1995 for his own personal use, to make various common web programming tasks easier and less repetitive and to track the visitors to his online resume.
In 1997, the software transformed from a personal development project into a professional development effort. The name originally stood for “Personal Home Page,” but has since become a recursive acronym, standing for PHP Hypertext Processor.
The goal of this release was to minimize the amount of code required to achieve results, which led to PHP being HTML centric–that is, PHP code was embedded inside HTML.
The second PHP release, known as PHP/F1 2.0 was the first to achieve wide spread popularity, and despite the parsing inconsistencies, it managed to attract a few converts.
The release of PHP 3 was largely driven by Zeev Suraski and Andi Gutmans, who rewrote PHP from the ground up and removed the parsing problems. PHP 3 also made it much easier for others to extend the language. PHP 3 has live up to the design goals of improving the performance of complex applications and modularity of PHP’S code base. Apart from this, it provides end users with a solid infrastructure for lots of different databases, protocols and APIs.
Its successor, PHP 4, contained numerous major changes, including Zend Engine. PHP 4 has introduced multi-threading, which essentially allows particularly lengthy, but non-critical functions to be run independently from the main script process, further streamlining execution.
The engine took over the core of PHP and introduced reference counting, whereby all resources used in scripts (database connections, files, etc) are tracked automatically by the engine, and freed when no longer used to minimize memory usage and ensure there were no memory leaks. In short, Zend engine, take a leading role in improving the performance of PHP scripts.
PHP 5 offers three different types of properties: public, protected and private properties. PHP 5 was released powered by the new Zend Engine II. PHP 5 included new features such as:
Support for object-oriented programming, better support for MYSQL, embedded support for SQlite and integrated SOAP support.
The PHP Data Objects extension, which defines a light weight and consistent interface for accessing databases.
Error handling via exceptions
Although not as vast as the jump from PHP 3 to PHP 4, the move from PHP 4 to PHP 5 is still a big one.
Along with hugely improved object orientation, the addition of try/catch error handling, and exceptions, there are two major new extensions: simple XML, a fast and easy-to-learn way to interact with XML documents, and SQLite, a new flat-file database API that eases the burden of deploying simple database solutions.