src/ArrayObject.php
public function add($element, $index = null) {
		if ($index === null) {
			$this->array[$this->count()] = $element;
		} else {
			array_splice($this->array, $index, 0, $element);
		}

		return $this;
	}
public function add($element, $index = null) {
		if ($index === null) {
			$this->array[$this->count()] = $element;
		} else {
			array_splice($this->array, $index, 0, $element);
		}

		return $this;
	}
public function add ( $ element , $ index = null ) { if ( $ index === null ) { $ this -> array [ $ this -> count ( ) ] = $ element ; } else { array_splice ( $ this -> array , $ index , 0 , $ element ) ; } return $ this ; }
Adds an element to that array

@param mixed $element
@param int $index
@return $this
Adds an element to that array