PHP Pocket Reference, 2nd Edition (2009)
PHP (PHP Hypertext Preprocessor) is a web scripting language. It was specifically designed to solve "the web problem." PHP is easy to learn because it builds on the bits and pieces that most people already know. The pieces that you don't know are filled in by excellent online documentation and many high-quality books. This simple approach to solving the web problem has caught on with an amazing number of people.
This pocket reference further simplifies things by focusing on the absolute essentials. It provides an overview of the main concepts needed for most web applications, followed by quick reference material for most of the main PHP functions.