PHP Validaton class: Validate submitted form values according to rules

This class can validate submitted form values according to rules.

It takes an array of parameters of rules and the $_POST or $_GET array with the submitted form values and verifies if they satisfy the specified rules.

The class returns a list of invalid form values in case some are invalid.

Currently it can validate values with rules like making the value required, maximum and minimum length, check if it is a number, letters or numbers only, email addresses, and URL.