Filter Class: Filter to prevent XSS, SQL injection, CSRF attacks

This package can filter values to prevent XSS, SQL injection, CSRF security attacks.

The main class can filter one value or an array of values by stripping HTML tags, adding slashes and escaping HTML entities.

Another class can prevent Cross-Site Request Forgery attacks by generating a secret token to be passed in forms, so it can verified later to avoid forms submitted by JavaScript code that executes automatically from other site pages.