code: private function prop_get_length():int {
  		$key = $this->iteratorKey;
  
  		$length = 0;
  		foreach($this as $element) {
  			$length++;
  		}
  
  		$this->iteratorKey = $key;
  		return $length;
  	}
docs: Returns the number of Elements contained in this Collection. Exposed as the
  $length property.
  @return int Number of Elements