<"no function";
    }
  }
  //如果需要指定类 (指定cat类，包含cat子类)
  function bose(cat $obj){
    $obj->fun();
  }
}
//抽象类
 abstract class animal{
  abstract function fun();
}
//cat猫类
class cat extends animal{
  function fun(){
    echo "cat say miaomiao...";
  }
}
//dog狗类
class dog extends animal{
  function fun(){
    echo "dog say wangwang...";
  }
}
class mouse extends cat{
}
//先new一个work类
$new_work = new work();
//然后通过new_work对象 调用 polymorphic 方法,传入不同的类实现 父类引用指向子类对象；接口引用指向实现接口的类对象(多态)。
$new_work->polymorphic(new cat());
echo '<br/>';
$new_work->polymorphic(new dog());
echo '<br/>';
//指定类方式仿java
$new_work->bose(new cat());
echo '<br/>';
//如果传输其他类，或者未继承cat类则会报错
//$new_work->bose(new dog());
echo '<br />';
//这也不会报错
$new_work->bose(new mouse());

cat say miaomiao...
dog say wangwang...
cat say miaomiao...

cat say miaomiao...