public static function getUsersData() { if (!self::$users_data) { $query = ' SELECT u.id , u.name , e.name education , e.id education_id , group_concat(c.name separator ", ") cities , concat(",",group_concat(c.id),",") cities_ids from users u left join educations e on e.id = u.education_id left join user_cities uc on uc.user_id = u.id left join cities c on uc.city_id = c.id group by u.id; '; self::$users_data = cDB::fetch($query, 'id'); } return self::$users_data; }