Inspekt is a PHP library that makes it easier to write secure web applications, which works on PHP 4 and 5 and has no external dependencies.

Inspekt acts as a sort of ‘firewall’ API between user input and the rest of the application. It takes PHP superglobal arrays, encapsulates their data in an “cage” object, and destroys the original superglobal. Data can then be retrieved from the input data object using a variety of accessor methods that apply filtering, or the data can be checked against validation methods. Raw data can only be accessed via a ‘getRaw()’ method, forcing the developer to show clear intent.

Inspekt can also be used on arbitrary arrays, and provides static filtering and validation methods.

Project Page: inspekt - Google Code
Downloads Page : http://code.google.com/p/inspekt/downloads/list