When might it be necessary to store a class object inside itself?

Question

PHP

The question is stupid, but I could not help but ask, it was very necessary. When might this be needed? Thanks for answers!

class MyClass
{
   public $class;
   public function __construct()
   {
       $this->class=new MyClass;
   }
}

Answer 1

When the constructor takes some arguments, they do so. Recursion.

Answer 2

Only when describing tree-like data structures. But not in the constructor, because in this case we get a recursive call to the object's constructor.