Yii: CGridView column with drop-down filter

cgridview-with-dropdown-filter.php

<?php $this->widget( 'zii.widgets.grid.CGridView', array(
	'id'             => 'product-2-group-grid',
	'dataProvider'   => $model->search(),
	'filter'         => $model,
	'summaryText'    => '{start} - {end} / {count}',
	'selectableRows' => 2,
	'columns'        => array(
		array(
			'name'        => 'product_code',
			'htmlOptions' => array( 'class' => 'product_code' ),
		),
		array(
			'name'        => 'product_name',
			'htmlOptions' => array( 'class' => 'product_name' ),
		),
		array(
			'name'        => 'group_title',
			'htmlOptions' => array( 'class' => 'group_title' ),
			'filter'      => CHtml::dropDownList( 'VwProductsList[group_title]', $model->group_title,
					CHtml::listData( ProductGroups::model()->findAll( array( 'order' => 'group_title' ) ), 'group_title', 'group_title' ),
					array( 'empty' => '-' )
				),
		),
	),
) ); ?>