protected function getFaceList()
    {
        if (!function_exists('face_detect')) {
            $msg = 'PHP Facedetect extension must be installed.
                    See http://www.xarg.org/project/php-facedetect/ for more details';
            throw new \Exception($msg);
        }

        if ($this->maxExecutionTime) {
            $timeBefore = microtime(true);
        }
        $faceList = $this->getFaceListFromClassifier(self::CLASSIFIER_FACE);
        if ($this->maxExecutionTime) {
            $timeSpent = microtime(true) - $timeBefore;
        }

        if (!$this->maxExecutionTime || $timeSpent < ($this->maxExecutionTime / 2)) {
            $profileList = $this->getFaceListFromClassifier(self::CLASSIFIER_PROFILE);
            $faceList = array_merge($faceList, $profileList);
        }

        return $faceList;
    }