Zend multiple where

I have thi next code, but he doesn't work:

$select_sell = $this->select();
$select_sell->from($this->_name, array('rank_id'))
            ->where('rank_id = ?', $id)
            ->where('type = ?', 'must_sell');
$result = $this->fetchAll($select_sell)-&开发者_运维技巧gt;count();

I need to make this query ... WHERE rank_id = $id AND type = 'must_sell'..

Thank toy.

---

As gordon said in his comment, type isn't a variable:

$select_sell = $this->select();
$select_sell->from($this->_name, array('rank_id'))
            ->where('rank_id = ?', $id)
            ->where('type = "must_sell"');
$result = $this->fetchAll($select_sell)->count();

---

Run into this problem a few times before. You can solve it like this

$select_sell = $this->select();
$select_sell->from($this->_name, array('rank_id'))
    ->where("(rank_id = $id AND type = 'must_sell')");