从受保护的属性中获取值

Question

我在访问受保护的财产时遇到问题。我正在尝试查询 wordpress 的数据库表。以下是我的代码：

    <?php
    $table_name = 'wp_wp_pro_quiz_question';
    $current_quiz_id = $wpdb->get_var("SELECT max(quiz_id) as quiz_id FROM $table_name");

    $results = $wpdb->get_results( "SELECT * FROM $table_name where quiz_id = $current_quiz_id");
  if(!empty($results)){
     foreach($results as $row){?>
     // print_r($row->answer_data);
     print_r(unserialize($row->answer_data));
     $answer_data = unserialize($row->answer_data);
     $answers = array();
     foreach($answer_data as $obj) {
     $answers[] = $obj->get_answer;
     }
     print_r($answers);
     }           
    ?>

print_r(unserialize($row->answer_data)) 给出以下结果：

Array ( 
[0] => WpProQuiz_Model_AnswerTypes Object ( [_answer:protected] => 26 [_html:protected] => 1 [_points:protected] => 1 [_correct:protected] => 1 [_sortString:protected] => [_sortStringHtml:protected] => 1 [_mapper:protected] => ) 
[1] => WpProQuiz_Model_AnswerTypes Object ( [_answer:protected] => 6 [_html:protected] => 1 [_points:protected] => 1 [_correct:protected] => [_sortString:protected] => [_sortStringHtml:protected] => 1 [_mapper:protected] => ) 
[2] => WpProQuiz_Model_AnswerTypes Object ( [_answer:protected] => 4 [_html:protected] => 1 [_points:protected] => 1 [_correct:protected] => [_sortString:protected] => [_sortStringHtml:protected] => 1 [_mapper:protected] => ) 
[3] => WpProQuiz_Model_AnswerTypes Object ( [_answer:protected] => 16 [_html:protected] => 1 [_points:protected] => 1 [_correct:protected] => [_sortString:protected] => [_sortStringHtml:protected] => 1 [_mapper:protected] => ) ) 

我使用 get 来访问受保护的字段。我将所有值推送到数组 $answers 中，但我得到的所有值都为空。 print_r($answers) 的结果： 数组 ( [0] => [1] => [2] => [3] => )

我在这里做错了什么？

谢谢

Answer 1

将两个选择替换为一个：

SELECT * FROM $table_name
    ORDER BY quiz_id DESC LIMIT 1

然后将* 替换为您想要的列列表。