public function prepare($sql)
{
$this->_connect();
$stmtClass = $this->_defaultStmtClass;
if (!class_exists($stmtClass)) {
require_once 'Zend/Loader.php';
Zend_Loader::loadClass($stmtClass);
}
$stmt = new $stmtClass($this, $sql);
$stmt->setFetchMode($this->_fetchMode);
return $stmt;
}