Introducing PHP
The current version of PHP is PHP4, which we call PHP throughout this book. The current release at the time of writing is 4.0.6.
PHP is a recursive acronym that stands for PHP: Hypertext Preprocessor; this is in the naming style of GNU, which stands for GNU's Not Unix and which began this odd trend. The name isn't a particularly good description of what PHP is and what it's commonly used for. PHP is a scripting language that's usually embedded or combined with HTML and has many excellent libraries that provide fast, customized access to DBMSs. It's an ideal tool for developing application logic in the middle tier of a three-tier application.