how insert method in class from another file? Now i get error:

C `T_FUNCTION ': \ wamp \ www \ hattında 9 index.php

    index.php file:
    <?php

    class cars
    {
        public function go()
        {
            echo 'go go';
        }    
        include('stop.php');
    }

    $c = new cars;
    $c->go();
    ?>

    stop.php file
    <?php
    public function stop()
    {
        echo 'stop method';
    }

?>