我想从post meta表中获取元键为“project\\u id”的所有数据。我写了一个查询，它应该在Theory中工作，但我无法看到我得到了什么，并且将这个查询注入我的插件不会生成任何东西。请查看此查询，并帮助我了解其是否正确，结果的格式是什么，如何回传以查看我得到的结果：

function mp_all_ids( ){
global $bp, $wpdb, $post;

$query = <<<QUERY
SELECT      project_id.post_id
FROM        $wpdb->postmeta project_id
LEFT JOIN  $wpdb->postmeta height 
            on height.post_id = project_id.post_id
            and height.meta_key = \'height\'
LEFT JOIN  $wpdb->postmeta width 
            on width.post_id = project_id.post_id
            and width.meta_key = \'width\' 
WHERE       project_id.meta_key = \'project_id\'
ORDER BY    project_id.meta_value+(0) ASC
QUERY;
$data = $wpdb->get_results( $query );

return apply_filters( \'mp_ids\', $data );
}

array(3) {
  [0]=>
  object(stdClass)#457 (1) {
    ["post_id"]=>
    string(3) "385"
  }
  [1]=>
  object(stdClass)#458 (1) {
    ["post_id"]=>
    string(3) "451"
  }
  [2]=>
  object(stdClass)#377 (1) {
    ["post_id"]=>
    string(3) "453"
  }
}