tyz910

<? 
class City {
    private $length;
    function __construct($length) {
        $this->length = $length;
    }
    public function getLength() {
        return $this->length;
    }
}

class Auto {
    private $speed;
    function __construct($speed) {
        $this->speed = $speed;
    }
    public function getSpeed() {
        return $this->speed;
    }
    public function howLongToGo($length) {
        return $length / $this->speed;
    }
    public function howLongToGoThrowCity(City $city) {
        return $city->getLength() / $this->speed;
    }
}

$a = new Auto(20);
$c = new City(100);

print $a->howLongToGo($c->getLength());
// Или так
print $a->howLongToGoThrowCity($c);