继承和委托关系

class Sanitation{
    public function  Washhands(){
        echo "Cleaning!";
    }    
}

class Child extends  Sanitation{
    
}


$child=new Child();

$child->Washhands();

class Sanitation{
    public function  Washhands(){
        echo "Cleaning!";
    }    
}

class Child  {
    private $sanitation;
    function __construct(){
        $this->sanitation=new Sanitation();
    }
    public function Washhands(){
        return $this->sanitation->Washhands();
    }
    
}


$child=new Child();
$child->Washhands();