protected function pushStack($funcName)
    {
        $this->funcStack[] = array(
            'function' => $funcName,
            'tsStart' => $this->timeLastTick,
            'subTime' => 0,         // how much time spent in nested functions
        );
        if (!isset($this->data[$funcName])) {
            $this->data[$funcName] = array(
                'calls' => 0,
                'totalTime' => 0,   // time spent in function and nested func
                'ownTime' => 0,     // time spent in function excluding nested funcs
            );
        }
        $this->data[$funcName]['calls'] ++;
    }