help function for pattern Follow

Hello !

I need a tip.
I want to work with design patterns. For example, the dependency pattern.
Here's an example.

----------------------

class model{

   public $subClass;

   public function setSubclass($objekt){
       $this->subClass = $objekt;
   }

}

class test{

  public function getInfo(){
    return 'my info';
  }

}

$model = new model();
$model->setSubclass(new test());
$info = $model->subClass->getInfo();

--------------------------------------

Unfortunately, the 'PhpStorm' not the autocompletion of the subclass.
Who can help?

Sincerely

Stephan