public function push($iElementID)
    {
        if (empty($iElementID)) {
            return $this->returnThis();
        }

        if ($this->isEmpty()) {
            $this->arElementIDList = [$iElementID];

            return $this->returnThis();
        }

        $this->arElementIDList[] = $iElementID;

        return $this->returnThis();
    }