下拉取决于yii框架中的多选下拉列表

I am new in Yii framework and I cannot solve this problem with dropdown.

In my page I have two dropdown lists, both of them multiselect dropdowns. And second one depends first dropdown. For example,

1-dropdown is fruits, vegetables, drinks;

2-dropdown depends user selection, if user select fruit and drinks, it should be display apple, grapes, juice, bier ( all together in one dropdownlist );

If user select only one option e.g vegetables in first dropdown, second should display onion, potato etc.

Here source code:

//---------- VIEW ------------

    <div id="left">
                        <div class="btn-group">
                            <?php             
                                echo CHtml::dropDownList('group', '', CHtml::listData($group,'group','group'), array(
                                    'multiple'=>'multiple',
                                    'ajax'=>array(
                                        'type' => 'POST',
                                        'url' => CController::createUrl('site/change'),
                                        'update' => '#e5'
                                    ),
                                    'id' => 'e4',
                                    'style' => 'width:300px'
                                ));
                            ?>
                        </div>
                    </div>
                    <div id="right">
                        <div class="btn-group">
                            <?php
                                echo CHtml::dropDownList('subgroup','', array(), array(
                                    'multiple' => 'multiple',
                                    'id'=>'e5',
                                    'style' => 'width:300px'
                                ));
                            ?>
                        </div>
                    </div>


// ------------ CONTROLLER ------------


public function actionChange()
        {

            $groupName = $_POST['group'];        


            $dpCriteria = new CDbCriteria();
            $dpCriteria->select = 'subgroups';
            $dpCriteria->condition = 'group = '.$groupName;

            $data = Subgroups::model()->findAll($dpCriteria);

            $data = CHtml::listData($data,'subgroups','subgroups');
            foreach($data as $value=>$name)
            {
                echo CHtml::tag('option',
                           array('value'=>$value),CHtml::encode($name),true); 
            }
        }

The method you are asking is Dependent Dropdown. YII framework have tutorials for creating Dependent Dropdown. Check this link for more details and examples

EDIT:

In your code, you are checking groupname with single value as 'group = '.$groupName;. But $groupname is an array of value. So you have use in in mysql with the values of imploded $groupname array.

Your condition in criteria is:

$dpCriteria->condition = 'group in ('.implode(",",$groupName).')';

Try like this.In your ajax array,

'update'=>'#'.CHtml::activeId($model,'attribute_to_update'),
'data'=>array('atribute'=>'js:this.value'),