Why interface

gistfile1.aw

<?php
interface Person {
    public function name();
    public function gender();
}

class Tom implements Person {
    // Must!!
    public function name() { /* do something... */ }
    public function gender() { /* do something... */ }
}

class Neo implements Person {
    // Must!!
    public function name() { /* do something... */ }
    public function gender() { /* do something... */ }

    // Custom by self
    public function love() { /* do something... */ }
}
?>