$id = (int)$_GET['id'];
            $place = $DB_con->prepare("SELECT * FROM `post` WHERE `category`=".$id."");
            $place->execute();
            foreach ($place->fetchAll() as $rawp){

            $mains = $DB_con->prepare("SELECT * FROM `place` WHERE `id`=".$rawp['placeid']."");
            $mains->execute();

            foreach ($mains->fetchAll() as $rawps){
            echo $rawps['id'].'<br/>';
            }

            }