Sort by foreign key relationship in cgridview

I have the following code:


<?php $this->widget('zii.widgets.grid.CGridView', array(

	'id'=>'passwords-grid',

	'dataProvider'=>$model->search(),

	'filter'=>$model,

	'columns'=>array(

 		array(

                        'name'=>'clients.name',

                        'filter'=>CHtml::listData(Clients::model()->findAll(), 'id', 'name'),

                ),

		'description',

		'url',

		'username',

		'password',

		'notes',


		array(

			'class'=>'CButtonColumn',

		),

	),

)); ?>

The code successfully implements a Client Name column and shows the client’s name (as opposed to their ID). However, I do not get a select dropdown in the header row like I would expect. Can someone shed some light into what I’m doing wrong here?

check this

http://www.yiiframework.com/forum/index.php?/topic/19913-cgridview-with-multiple-models/page__view__findpost__p__98809