API buat filter data

public static function FILTERVOUCHER($voucherfilter, $filter) {
    header('content-type:application/json;charset=UTF-8');

    $criteria = new CDbCriteria();
    if($filter == 'kosong') {
        if($voucherfilter == 'NOTUSED') {
            $criteria->compare('merchant_code_exp', 0);
        } else {
            $criteria->compare('merchant_code_exp', 1);
        }
    } else {
        if($voucherfilter == 'NOTUSED') {
            $criteria->compare('merchant_id', $filter);
            $criteria->compare('merchant_code_exp', 0, true, 'AND');
        } else {
            $criteria->compare('merchant_id', $filter);
            $criteria->compare('merchant_code_exp', 1, true, 'AND');
        }
    }

    $criteria->order = 'id ASC';
    $model = MerchantBatchCode::model()->findAll($criteria);
    $ConvToJSON = CJSON::encode($model);

    echo '{"items":'.$ConvToJSON.'}';
    Yii::app()->end();
}