zend framework 1 zend_db result the same in different condition

My problem is, when i want to read datas from database with zend framework 1, I get the exactly same result even if i use different conditions.
My table named 'maps' contains 2 rows:

id: 1 date: date1 description: sth1 userid: 30  
id: 2 date: date2 description: sth2 userid: 30

application.ini:

resources.db.params.charset = "utf8"  
resources.db.adapter = pdo_mysql  
resources.db.params.host = localhost  
resources.db.params.username = root  
resources.db.params.password =  
resources.db.params.dbname = gallery  

in my controller:

$gallery = new Gallery_Model_DbTable_Maps();  
$maps = $gallery->getMaps($user_id);  
$this->view->datas = array(
     'maps' => $maps,
);

in my model:

class Gallery_Model_DbTable_Maps extends Zend_Db_Table_Abstract  
{  
    protected $_name = 'maps';  
    public function getMaps($id){  
        $select = $this->select();  
        $select->where('userid = ?', $id);  
        $rows = $this->fetchAll();  
        return $rows->toArray();  
    }  
}

If I replace the "$id" to something else than 30 in "Gallery_Model_DbTable_Maps" I always get the 2 rows mentioned above... If I change the function for this...

 public function getMaps($id){  
    $dbAdapter = Zend_Db_Table::getDefaultAdapter();
    $stmt = $dbAdapter->query('SELECT * FROM maps WHERE userid = 32');
    $rows = $this->fetchAll()->toArray();
    return $rows;
 }

...the problem still occurs, and get the same result. But if i run the query in the phpmyadmin, everything is fine

And one additional think(maybe help to find out what is the problem), if i use joins, the joined table datas doesn't appear in the result(in zf structure), but if i run this query(containing join) in phpmyadmin, everything is fine.