stderr：PHP警告：从空值创建默认对象

Question

(stderr: PHP Warning:  Creating default object from empty value in /ww_work/base/exam_class.php on line 1785,)

我没有php程序员，但apache日志正在使用以下函数中的空值数组创建默认对象。

// this function put exam answer by student ito exm object.
// it also give the score to question if answer was correct.
public function put_answer($question_id,$answer_id){

    $this->given_answer[$question_id]=$answer_id;

    $question_obj = $this->questions[$question_id];
    //$answer_obj = new stdClass();
    $answer_obj = $question_obj->answer[$answer_id];
    $answer_obj->given_answer="Y";

    if(($answer_obj->given_answer==="Y")&&($answer_obj->correct_answer==="Y")){
        $question_obj->given_mark=$given_mark + $question_obj->score;
        $question_obj->given_answer=$answer_id;
        $question_obj->question_result="right";
    }else{
        $question_obj->given_mark=$given_mark + 0;
        //$answer_obj->given_answer="N";
    }

}

正在$answer_obj->given_answer="Y";行生成错误。

做一些谷歌搜索，我认为这可能是松散的连接 （Creating default object from empty value in PHP?）

但是如果有人对如何删除此警告有任何想法，除了关闭php警告之外，我们将不胜感激。