protected function get_array_of_placeholders($question) {
        $qtext = $question->questiontext;
        $error = '<b> ERROR</b>: Please check the form for this question. ';
        if (!$qtext) {
            echo $error . 'The question text is empty!';
            return false;
        }

        // Get the slots.
        $slots = $this->getEmbeddedTextArray($question);

        if (!$slots) {
            echo $error . 'The question text is not in the correct format!';
            return false;
        }

        $output = array();
        foreach ($slots as $slot) {
            $output[] = substr($slot, 2, strlen($slot) - 4); // 2 is for '[[' and 4 is for '[[]]'.
        }
        return $output;
    }