Stupid question

I have the following:

$dsn = "mysqli://$username:$password@$hostname2/$database";
$options = array(
     'debug' => 3,
     'result_buffering' => false,
   );
   $dbh =& MDB2::factory($dsn, $options);
         if (PEAR::isError($mdb2))
         {
                 die($mdb2->getMessage());
         }




function tallyCart($_u_id,$dbh){
        while($row = $result->fetchrow(MDB2_FETCHMODE_ASSOC)) {
                 $_showCheckOut=1;
                 $_pdetail=new ProductDetail($row{'product_ID'}, 
$row{'product_Quantity'}, $_u_id);
                  $_getSubTotal += $_pdetail->_subTotal;
                  $_counter++;
         }
}

I'm getting:  Call to undefined method MDB2_Error::fetchrow()

anyone have any ideas?  Can I not pass a database handle to a function?

Thanks,
Curtis