'buttonID' => array
(
    'label'=>'...',     //Text label of the button.
    'url'=>'...',       //A PHP expression for generating the URL of the button.
    'imageUrl'=>'...',  //Image URL of the button.
    'options'=>array(), //HTML options for the button tag.
    'click'=>'...',     //A JS function to be invoked when the button is clicked.
    'visible'=>'...',   //A PHP expression for determining whether the button is visible.
)