The PHP Functions Essential Reference is a simple, clear and authoritative function reference that clarifies and expands upon PHP's existing documentation.The authors have spent time evaluating all of the PHP functions and have selected the essential functions to include in the printed book. This includes around 900 of the 1500 functions. The remaining functions will be covered in the same depth and treated in the same way, but they will appear on the newriders.com web site along with the content of the entire book, which is provided under the OPL.