[Yii Cgridview How To Access Id For Each Column]

I am using a CGridView with CActiveDataProvider. Everything works fine however now I have a need to show a custom button depending upon the id of the row.

I can add the button and get it to work as well however I cannot customise the image according to the row id. I can see from examples that when creating url I can access the id of row by calling $data->id however when I try to do that for imageURL it does not work. My code is below:

$this->widget('zii.widgets.grid.CGridView', array(
		'dataProvider'=>$model->search(),
		'filter'=>$model,
		'columns'=>array(
				'id',
				'name',
				'desc',
				'created',
				array(
						'class'=>'CButtonColumn',
						'header'=>'Active State',
						'template'=>'{rank}',
						'buttons'=>array(
								'rank'=>array(
										'label'=>'Rank',											  
										'imageUrl'=>$this->getRank($data->id),
										'url'=>'Yii::app()->createUrl("users/updateRank", array("id"=>$data->id))',
										'options'=>array(
												'ajax'=>array(
														'type'=>'POST',
														'url'=>"js:$(this).attr('href')",															  
												),
										),
								),
						),					
				),					
		),
));

Image URL calls a function in my controller which returns a url to the image. However I cannot pass the id of the current record user is clicking upon and I always get the default image back. If I use $data->id I get an error that data does not exist. If I use $this->id it is referring to the controller and I get the controller id. Anyway I can get the id of the row and pass it over to a function.