Export data to a CSV/Excel file:

//...
use yii\filters\AccessControl;
use yii\filters\VerbFilter;
use yii\helpers\Html;
 
class ItemController extends Controller
{
    public function behaviors()
    {
        return [
            'access' => [
                'class' => AccessControl::className(),
                'rules' => [
                    [
                        'actions' => [/* ... */ 'export'],
                        'allow' => true,
                        'roles' => ['@'],  // @ = Authenticated users
                    ],
                ],
            ],
            //...
        ];
    }
 
    //...
 
    public function actionExport($format='csv')
    {
        switch($format) {
            case 'excel':
                $this->actionExportExcel();
                break;
 
            case 'csv':
            default:
                $this->actionExportCsv();
                break;
        } // endswitch
    }
 
    public function actionExportExcel()
    {
        $model = Item::find()->All();
 
        $filename = 'Data-'.Date('YmdGis').'-Items.xls';
        header("Content-type: application/vnd-ms-excel");
        header("Content-Disposition: attachment; filename=".$filename);
 
        echo '<table border="1" width="100%">
            <thead>
                <tr>
                    <th>id</th>
                    <th>name</th>
                    <th>description</th>
                    <th>created</th>
                    <th>modified</th>
                    <th>status</th>
                    <th>user_id</th>
                </tr>
            </thead>';
        foreach($model as $data){
            echo '
                <tr>
                    <td>'.Html::encode($data['id']).'</td>
                    <td>'.Html::encode($data['name']).'</td>
                    <td>'.Html::encode($data['description']).'</td>
                    <td>'.Html::encode($data['created']).'</td>
                    <td>'.Html::encode($data['modified']).'</td>
                    <td>'.Html::encode($data['status']).'</td>
                    <td>'.Html::encode($data['user_id']).'</td>
                </tr>
            ';
            //<td><img src="'.Yii::$app->request->baseUrl.'/uploads/'.$data['foto'].'" width="100px"></td>
        }
        echo '</table>';
    }
 
    public function actionExportCsv()
    {
        $model = Item::find()->All();
 
        $filename = 'Data-'.Date('YmdGis').'-Items.csv';
        header("Content-type: text/csv");
        header("Content-Disposition: attachment; filename=".$filename);
 
        echo "id,name,description,created,modified,status,user_id\n";
        foreach($model as $data){
            echo $this->getCsvField($data['id']);
            echo ',' . $this->getCsvField($data['name']);
            echo ',' . $this->getCsvField($data['description']);
            echo ',' . $this->getCsvField($data['created']);
            echo ',' . $this->getCsvField($data['modified']);
            echo ',' . $this->getCsvField($data['status']);
            echo ',' . $this->getCsvField($data['user_id']) . "\n";
        }
    }
 
    private function getCsvField($field)
    {
        return ( (strpos($field, "'") !== false) ? "'".$field."'" : $field );
    }
}

    // Usage:
    //     actionOutputCSV([
    //         ["Car1", "Car2", "Car3"],
    //         ["Volvo 1", "BMW 1", "Toyota 1"],
    //         ["Volvo 2", "BMW 2", "Toyota 2"],
    //         ["Volvo 3", "BMW 3", "Toyota 3"],
    //     ],'download.csv');
    // Source: See more at: https://arjunphp.com/create-download-csv-files-php/#sthash.f6JCTy4J.dpuf
    function actionOutputCSV($data, $file_name = 'file.csv')
    {
        // Output headers so that the file is downloaded rather than displayed
        header("Content-Type: text/csv");
        header("Content-Disposition: attachment; filename=$file_name");
        // Disable caching - HTTP 1.1
        header("Cache-Control: no-cache, no-store, must-revalidate");
        // Disable caching - HTTP 1.0
        header("Pragma: no-cache");
        // Disable caching - Proxies
        header("Expires: 0");
 
        // Start the ouput
        $output = fopen("php://output", "w");
 
        // Then loop through the rows
        foreach ($data as $row) {
            // Add the rows to the body
            //fputcsv($output, $row); // here you can change delimiter/enclosure
            fputcsv($output, $row, "\t"); // here you can change delimiter/enclosure
        }
        // Close the stream off
        fclose($output);
    }
 
    // Usage:
    //     actionOutputExcel([
    //         ["Car1", "Car2", "Car3"],
    //         ["Volvo 1", "BMW 1", "Toyota 1"],
    //         ["Volvo 2", "BMW 2", "Toyota 2"],
    //         ["Volvo 3", "BMW 3", "Toyota 3"],
    //     ], ["Car1", "Car2", "Car3"], 'download.xls');
    // 
    function actionOutputExcel($data, $fields, $file_name = 'file.xls')
    {
        // Output headers so that the file is downloaded rather than displayed
        header("Content-type: application/vnd-ms-excel");
        header("Content-Disposition: attachment; filename=".$file_name);
 
        // Disable caching - HTTP 1.1
        header("Cache-Control: no-cache, no-store, must-revalidate");
        // Disable caching - HTTP 1.0
        header("Pragma: no-cache");
        // Disable caching - Proxies
        header("Expires: 0");
 
        // Start the ouput
        $output = fopen("php://output", "w");
 
        fwrite($output, '<table border="0" width="100%">'."\n");
 
        if (!empty($fields) && count($fields) > 0) {
            // Add the fields row to the body
            fwrite($output, "<thead>\n");
            fwrite($output, "<tr>\n  <th>");
            fwrite($output, implode("</th>\n  <th>", $fields));
            fwrite($output, "</th>\n</tr>\n");
            fwrite($output, "</thead>\n");
        }
 
        // Loop through the rows of data
        foreach ($data as $row) {
            // encode for HTML entities
            foreach ($row as $key => $cell) {
                $row[$key] = Html::encode($cell);
            }
 
            // Add the data rows to the body
            fwrite($output, "<tr>\n  <td>");
            fwrite($output, implode("</td>\n  <td>", $row));
            fwrite($output, "</td>\n</tr>\n");
        }
 
        fwrite($output, '</table>');
 
        // Close the stream off
        fclose($output);
    }

Using PHPExcel, we can export data to Excel native format. Add the following to the require section in the [app]/composer.json file:

"phpoffice/phpexcel": "*"

Perform a composer update:

$composer update

Files should be copied to vendor/phpoffice/phpexcel folder.

Add actions to your controller:

class PriceController extends Controller
{
    //...
 
    public function actionDownloadSample($file_name = 'file.xls')
    {
         $fields = ["item_code", "description", "cost"];
 
         $data = [
               $fields,
               ["prod_Mazda", "Mazda", "26000"],
               ["prod_Toyota", "Toyota", "24000"],
         ];
 
         $path_parts = pathinfo($file_name);
         switch($path_parts['extension']) {
            default:
            case 'csv':
                //...
                break;
 
            case 'html':
                //...
                break;
 
            case 'xls':
                $this->actionOutputExcel($data, $file_name);
                break;
        }
    }
 
    function actionOutputExcel($data, $file_name = 'file.xls')
    {
        date_default_timezone_set('America/Los_Angeles');
 
        $docExcel = new \PHPExcel();  // requires \vendor\phpoffice\phpexcel\Classes\PHPExcel
        $docExcel->setActiveSheetIndex(0);
        $docExcel->getActiveSheet()->fromArray($data, null, 'A1');
 
        header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
        header('Content-Disposition: attachment;filename="'.$file_name.'"');
        header('Cache-Control: max-age=0');
 
        // Output data
        $writer = \PHPExcel_IOFactory::createWriter($docExcel, 'Excel5');
        $writer->save('php://output');
    }
}    

In your view, call it like this:

<?php
use yii\helpers\Html;
//...
 
?>
 
 
<!-- Download Sample Button -->
<div class="btn-group">
<?= Html::a('<i class="glyphicon glyphicon-download d-icon"></i> ' . Yii::t('app', 'Download Sample') . ' <span class="caret">',
    '#', 
    ['class' => 'btn btn-default dropdown-toggle', 'data-toggle'=>"dropdown", 'role'=>"button", 'aria-haspopup'=>"true", 'aria-expanded'=>"false"]
) ?>
  <ul class="dropdown-menu">
    <li><?= Html::a(Yii::t('app', 'CSV Format'),     ['download-sample', 'file_name' => 'prices-audina.csv'],  ['class' => '', 'data-pjax' => '0']) ?></li>
    <li><?= Html::a(Yii::t('app', 'Excel Format'),   ['download-sample', 'file_name' => 'prices-audina.xls'],  ['class' => '', 'data-pjax' => '0']) ?></li>
    <li><?= Html::a(Yii::t('app', 'HTML Format'),    ['download-sample', 'file_name' => 'prices-audina.html'], ['class' => '', 'data-pjax' => '0']) ?></li>
  </ul>
</div>

• Import and Export Data Using PHPExcel