How can i set the header of CGridView with a php value

<?php
$this->widget('zii.widgets.grid.CGridView', array(
    'id' => 'grant-approval-child',
    'dataProvider'=>$grantRequestItems,
    'ajaxUpdate' => true,
    'enableSorting' => true,
    'emptyText' => '&nbsp;',
    'itemsCssClass' => 'table table-hover table-grant-approval',
    'columns'=>array(
        [
            'header'=>'Last Update',
            'name' => 'requestLastUpdated',
            'value'=>'$data["requestLastUpdated"]',
        ],
        [
            'name' => 'status',
            'header' => 'Approval Status and Chat',
            'headerHtmlOptions' => ['class' => 'text-center'],
            'type' => 'raw',
            'value' => function($data) {
		return "<span>" . (($data['approval'] == 1)? "Approved" : "Pending Your Approval") . "</span></br> <span class='glyphicon glyphicon-comment show-chat' data-entity-id='" . $data['requestId'] . "' data-entity-type='grant'></span>";
            },
            'htmlOptions' => ['class' => 'text-center'],
        ],
        [
            'header'=>'Submitted by*',
            'name' => 'fullName',
            'value'=>'$data["fullName"]',
        ],
        [
            'header'=>'Associated Campus',
            'name' => 'campus',
            'value'=>'$data["campus"]',
        ],
        [
            'header'=>CHtml::encode($data["question_1"]["question_response"]),
            'name' => 'question_1',
            'type' => 'raw',
	    'value'=> function($data) {
		return "<div>" . $data["question_1"]["question_response"] . "</div>";
	    }
        ],
        [
            'header'=>'123',
            'name' => 'question_2',
            'type' => 'raw',
	    'value'=> function($data) {
		return "<div>" . $data["question_2"]["question_response"] . "</div>";
	    }
        ],
        [
            'header'=>'$q1',
            'name' => 'question_3',
            'type' => 'raw',
	    'value'=> function($data) {
		return "<div>" . $data["question_3"]["question_response"] . "</div>";
	    }
        ],
        [
            'header'=>'$q1',
            'name' => 'question_4',
            'type' => 'raw',
	    'value'=> function($data) {
		return "<div>" . $data["question_4"]["question_response"] . "</div>";
	    }
        ],
        [
            'header'=>'$q1',
            'name' => 'question_5',
            'type' => 'raw',
	    'value'=> function($data) {
		return "<div>" . $data["question_5"]["question_response"] . "</div>";
	    }
        ],
    ),
));

This is my code and i need my header to have the value $data[“question_no”][“question”] but it doesnt work if i directly put it to header. I am pretty new to Yii… so what can be done?