The Input class fetches data from GET, POST, COOKIE or SERVER and offer methods for validation and sanitation.

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

$name = $Input->get ('name')->apply_filters (FILTER_VALIDATE_STRING);
 
if ($name->is_valid()
    // 'name' is validated as string, but let's check some more.
 
    if ($name->validate ('is_alnum')) {
        // 'name' is now validated as an alpha-numerical string
    }
}