PHP Script Parser: Parse PHP scripts to detect usage bugs

This class is meant to parse a PHP script to determine how each variable is used and detect eventual bugs.

Note that this class just points probable misusage of the variables. You still have to check the code to confirm whether it is really a bug or a false bug report.

This class is capable of telling:

* Name of the variables
* Number of uses
* Number of assigments, operations, comparisions, concatenations, use as a subitem, use as an object, use as an array, or as a parameter.
* It presents the possible warning or error that found in the code.