Make it for PHP 5
It should be lightweight and you don't have to write much code
My idea is to make class Validate, where all checking methods, properties are.
1. Takes data from array POST/GET(REQUEST don't need i think
2. Use __set and __get functions to but field properties like this $new->name.
3. Checks the data $new->name->isString()->empty(); so on.
3. make custom exception handler to get errors.