USING KARTIK GRID VIEW FOR EXPORTING GRID

Add this in views/index.php

use yii\helpers\Html;
use yii\widgets\Pjax;
use kartik\grid\GridView;
use yii\helpers\ArrayHelper;
use backend\models\Studentuser;
use kartik\export\ExportMenu;

<?php
 $gridColumns = [
 //['class' => 'yii\grid\SerialColumn'],
 ['class' => 'kartik\grid\SerialColumn'],
 [
 'attribute'=>'studentuser_studentNo ',
 'label'=>'Student No.',
 'vAlign'=>'middle',
 'width'=>'190px',
 'value'=>function ($model, $key, $index, $widget) { 
 return Html::a($model->studentuser_studentNo, '#', []);
 },
 'format'=>'raw'
 ],
 'studentLastName',
 'studentFirstName',
 'semester',
 'schoolYear',
 'coursesWithProctoredExam',
 'typeOfExam',
 'examDate',
 [
 'attribute' => 'listofvenues.displayname',
 'format' => 'text',
 'label' => 'Exam Venue',
 ],
 ['class' => 'kartik\grid\ActionColumn'],
 
];

?>

<?= GridView::widget([
 'dataProvider' => $dataProvider,
 'columns' => $gridColumns,
 // 'export' => [
 // 'fontAwesome' => true,
 // ]
 'floatHeader'=>true,
 'floatHeaderOptions'=>['scrollingTop'=>'50'],
 'showPageSummary' => true,

'toolbar' => [
 [
 'content'=>
 Html::button('<i class="glyphicon glyphicon-plus"></i>', [
 'type'=>'button', 
 'title'=>Yii::t('kvgrid', 'Apply for Exam'), 
 'class'=>'btn btn-success'
 ]) . ' '.
 Html::a('<i class="glyphicon glyphicon-repeat"></i>', ['grid-demo'], [
 'class' => 'btn btn-default', 
 'title' => Yii::t('kvgrid', 'Reset Grid')
 ]),
 ],
 '{export}',
 '{toggleData}'
 ],

'panel' => [
 'heading'=>'<h3 class="panel-title"><i class="glyphicon glyphicon-globe"></i>Exam Application</h3>',
 'type'=>'success',
 'before'=>Html::a('<i class="glyphicon glyphicon-plus"></i> Apply for an Exam', ['create'], ['class' => 'btn btn-success']),
 'after'=>Html::a('<i class="glyphicon glyphicon-repeat"></i> Reset Grid', ['index'], ['class' => 'btn btn-info']),
 'footer'=>false
 ],

]); ?>

Add this to config/main.php

'modules' => [

'gridview' => [
 'class' => '\kartik\grid\Module',
 // your other grid module settings
 ],
 'gridviewKrajee' => [
 'class' => '\kartik\grid\Module',
 // your other grid module settings
 ],],