PHP5: reference to objects

I am writing multiple object classes in php that can point to each other using the repository class (to avoid too many database queries using the local object repository):

class Foo
{
    public $fooId;
    public $bar;
    function __construct($entity_id)
    {
        /**
        * Some Database stuff to get Foo object based on $entity_id
        **/
        $this->bar = Repository::get('Bar', $databaseStuff->barId);
    }
}

class Bar
{
    public $foo;
    function __construct($entity_id)
    {
        /**
        * Some Database stuff to get Bar object based on $entity_id
        **/
        $this->bar = Repository::get('Bar', $databaseStuff->barId);
    }
}

class Repository
{
    private static $entities = [];
    /**
     * @param string $entity_name
     * @param int $entity_id
     * @return mixed
     */
    public static function &get($entity_name, $entity_id)
    {
        $entity_name = ucfirst(strtolower($entity_name));
        if(!isset(self::$entities[$entity_name][$entity_id]))
        {
            self::$entities[$entity_name][$entity_id] =& $entity_name($entity_id);
        }
        return self::$entities[$entity_name][$entity_id];
    }
}

$foo = new Foo(1337);

      

        
        
        
      

    

The problem is that I get a kind of timeout / stack overflow, probably due to the fact that it $foo->bar

is a reference to the Bar object, but $bar->foo

is a reference to a Foo object, etc.

• I didn't forget to declare that my function returns a reference using & get (), am I right?
• My class is instantiated using the = & operator.

What could be wrong in my code (or my logic)? Thank.