我试图通过扩展wpdb类并覆盖自定义查询函数来获取带有回溯的查询数据。如果我创建db的符号链接，代码运行良好。php，但如果我尝试在插件文件中执行它，则无法直接工作。

代码为：

<?php

if ( ! defined( \'SAVEQUERIES\' ) ) {
  define( \'SAVEQUERIES\', true );
}

class My_DB extends wpdb {
  function __construct( $dbuser, $dbpassword, $dbname, $dbhost ) {
    parent::__construct( $dbuser, $dbpassword, $dbname, $dbhost );
  }

  function query( $query ) {
    if ( ! $this->ready ) {
      if ( isset( $this->check_current_query ) ) {
        $this->check_current_query = true;
      }
      return false;
    }

    if ( $this->show_errors ) {
      $this->hide_errors();
    }

    $result = parent::query($query);
    $result = parent::query( $query );
    if ( ! SAVEQUERIES ) {
      return $result;
    }

    $i = $this->num_queries - 1;
    $this->queries[$i][3] = debug_backtrace(false);
    $this->queries[$i][4] = $this->time_start;
    $this->queries[$i][5] = $result;

    return $result;
  }
}

$wpdb = new My_DB( DB_USER, DB_PASSWORD, DB_NAME, DB_HOST );

?>