您可以使用WP\\u Query：：get方法获取元查询中的任何内容，如下所示：

add_action(\'pre_get_posts\',\'add_another_meta_query\');

function add_another_meta_query($query){
  //Be sure to only use the main query on frontend
  if($query->is_main_query() && !is_admin()){
    $meta_query = $query->get(\'meta_query\',array());
    $new_meta_query = array();
    //now, $meta_query has the meta_query if set (or an array)
    //check if the old version of meta_query is used
    if($meta_key = $query->get(\'meta_key\',NULL)){
       $old_type_of_meta = array();
       $old_type_of_meta[\'key\'] = $meta_key;
       $query->unset(\'meta_key\');
       if($meta_value = $query->get(\'meta_value\',NULL)){
        $old_type_of_meta[\'value\'] = $meta_value;
        $query->unset(\'meta_value\');
       } elseif($meta_value = $query->get(\'meta_value_num\',NULL)){
         $old_type_of_meta[\'value\'] = $meta_value;
         $query->unset(\'meta_value_num\');
       } else {
         $old_type_of_meta[\'compare\'] = \'EXISTS\';
       }
       if($meta_compare = $query->get(\'meta_compare\',NULL)){
         $old_type_of_meta[\'compare\'] = $meta_compare;
         $query->unset(\'meta_compare\');
       }
       if($meta_type = $query->get(\'meta_type\',NULL)){
        $old_type_of_meta[\'type\'] = $meta_type;
        $query->unset(\'meta_type\');
       }
       $new_meta_query[] = $old_type_of_meta;
       if($orderby = $query->get(\'orderby\')){
         if(!is_array($orderby)){
            $orderby = str_replace(array(\'meta_value\',\'meta_value_num\'),array($meta_key,$meta_key),$orderby);
            $query->set(\'orderby\',$orderby);
         }
       }
    }
    if(isset($meta_query[\'relation\'])){
        //there is a special relation set within the meta_query.
        //to preserve this, we have to encapsulate the old meta queries
        $new_meta_query[] = $meta_query;
    } else {
       //there is no special relation set on global level ("AND" is used)
       //we can just merge them all together
       foreach($meta_query as $old_single_meta_query){
          $new_meta_query[] = $old_single_meta_query;
       }
    }
    //now we got all the "old" meta_queries in our $new_meta_query array.
    //let\'s add our own!
    $new_meta_query[] = array(
                        \'key\' => \'my_awesome_meta_key\',
                        \'value\' => \'whatever_i_need\',
                        \'compare\' => \'=\',
                        \'type\' => \'\',
                        );  
    //Last but not least: put it back into the $query
    $query->set(\'meta_query\',$new_meta_query); 
  }
}