自定义CFormModel的Yii验证规则不起作用

我有这个cformmodel:

<?php
class CombinationForm extends CFormModel {
    public $a;
    public $b;
    public $c;
    public $d;
    public $e;
    public $f;
    public function rules() {
        return array(
            array('a, b, c, d, e, f', 'required'),
            array('a, b, c, d, e, f', 'numerical', 'integerOnly' => true),
        );
    }
}

当用户输入字母而不是数字时，我希望使用ajax来捕捉错误。

这就是行动：

    public function actionIndex() {
        $model_combination_form = new CombinationForm();
        $this->performAjaxValidation($model_combination_form);
        if (isset($_POST['CombinationForm'])) {
//            echo '<pre>';
//            print_r($_POST['CombinationForm']);
//            echo '</pre>';
        }
        $this->render('combination_form', array(
            'model_combination_form' => $model_combination_form,
        ));
    }

它本应该触发ajax验证，但它没有。

这是形式：

<div style="position:relative;float:left;">
    <?php
    $form = $this->beginWidget('CActiveForm', array(
        'id' => 'combination-form',
        'enableAjaxValidation' => false,
    ));
    ?>
    <?php echo $form->errorSummary($model_combination_form); ?>
    <div style="float:left;padding:5px 5px;">
        <?php echo $form->textField($model_combination_form, 'a', array('style' => 'width:20px;')); ?>
    </div>
    <div style="float:left;padding:5px 5px;">
        <?php echo $form->textField($model_combination_form, 'b', array('style' => 'width:20px;')); ?>
    </div>
    <div style="float:left;padding:5px 5px;">
        <?php echo $form->textField($model_combination_form, 'c', array('style' => 'width:20px;')); ?>
    </div>
    <div style="float:left;padding:5px 5px;">
        <?php echo $form->textField($model_combination_form, 'd', array('style' => 'width:20px;')); ?>
    </div>
    <div style="float:left;padding:5px 5px;">
        <?php echo $form->textField($model_combination_form, 'e', array('style' => 'width:20px;')); ?>
    </div>
    <div style="float:left;padding:5px 5px;">
        <?php echo $form->textField($model_combination_form, 'f', array('style' => 'width:20px;')); ?>
    </div>
    <div style="float:left;padding:5px 5px;">
        <?php echo CHtml::submitButton('Genereaza'); ?>
    </div>
    <?php $this->endWidget(); ?>
</div>
<div style="clear:both;"></div>