===== Widok =====
<code php>
<?php

use kartik\export\ExportMenu;

$test='Test';
$gridColumns = [
    'id',
    ['attribute' => 'imie',
        'exportMenuStyle' => function() {
            return ['font' => ['bold' => true, 'color' => ['argb' => 'FF4F81BD']]];
        }
    ],
    'nazwisko',
    ['attribute'=>'test',
      'value'=>function() use ($test){
        return $test;
      }],
   
];

// Renders a export dropdown menu
echo ExportMenu::widget([
    'dataProvider' => $dataProvider,
    'columns' => $gridColumns,
    
    'boxStyleOptions' => [
        ExportMenu::FORMAT_EXCEL_X => [
            'borders' => [
                'outline' => [
                    'borderStyle' => 'none',
                ],
                'inside' => [
                    'borderStyle' => 'none',
                ],
            ],
        ],
    ],
    'exportContainer' => [
        'class' => 'btn-group mr-2'
    ],
    'dropdownOptions' => [
        'label' => 'Export',
        'class' => 'btn btn-outline-secondary',
    ],
    'filename' => 'testexp',
]);
</code>

===== Controller =====

<code php>
use yii\data\ActiveDataProvider;
...

public function actionIndex() {
        $dataProvider = new ActiveDataProvider([
            'query' => User::find()
                    
        ]);
        
        
        return $this->render('index', [
                    'dataProvider' => $dataProvider,
        ]);

    }
</code>