Although PHP is not a strong-typed language, PHP 5 does support type hinting for complex data types (objects) get_gas(); } } class pinto { function fill(pump $pump) { echo $pump->get_gas(); } } $pinto = new pinto; $pinto->fill(new premium); $pinto->fill(new regular); $mercedes = new mercedes; $mercedes->fill(new premium); $mercedes->fill(new regular); ?>]]>