Lesson 1 多态
class Human{ public function speak(){ echo "human can speak!"; } } class American extends Human{ public function speak(){ echo "speak engilsh!"; } } class Chinese extends Human{ public function speak(){ echo "speak Chinese!"; } } class client{ public static function call($input){ $input->speak(); } public static function say(Human $input){ $input->speak(); } } client::call(new Human()); client::call(new Chinese()); client::call(new American()); class Cat{ public function speak(){ echo "Cat speak!"; } } client::call(new Cat());