$addid = mysqli_query($link,"INSERT INTO 'wp_postmeta' ('post_id', 'meta_key', 'meta_value') VALUES($id, 'medafi_5ced1ba27d9ec', $id )")or die("Ошибка " . mysqli_error($link));
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''wp_postmeta' ('post_id', 'meta_key', 'meta_value') VALUES(15, 'medafi_5ced1ba27d9ec',' at line 1