The Input_Item class filters the GPCS data.

// Initiate class
$Input = new Input;
 
// fetches the key 'name' from GET
// initiates Input_Item and returns the object
$name = $Input->get ('name');
 
// $name is now an instance of Input_Item
 
echo 'Hello, ', $name->value ('Guest'); // prints 'Guest' if 'name' is not set or invalid.

$age = $Input->get ('age')->apply_filters (FILTER_VALIDATE_INT);
 
if ($age->is_valid()
    // 'age' is validated as an integer
 
    if ($age->validate ('in_range', array ('min' => 18, 'max' => 110))) {
        // the person is within the age 18-110
    }  
}