Set CSS property in CodeIgniter helper

For example I want to add display:none in a button in   CodeIgniter helper:
       echo helper::generateHTMLButton('addPadRankButton', 'Add', array('disabled'=>'disabled', 'id'=>'','style'=>'display:none', 'class' => 'addPadRankButton'));

Using  'style'=>'display:none' in last parameter (array)  of helper function to set CSS style.