wordpress template code for CSV export based on https://www.gloomycorner.com/export-data-to-csv-in-wordpress-with-php/

Wordpress template for CSV export

<?php  /*template name: Export*/

if ( !is_user_logged_in() ) {
    auth_redirect();
}
$admin_user = current_user_can('manage_options');
if (!$admin_user) die("ACCESS DENIED");

if (isset($_GET['export'])) {
    $table_head = array('column1', 'column2', 'column3');
    $table_body = array(
        array('a', 'b', 'c'),
        array('d', 'e', 'f')
    );

    $csv = implode( $table_head, ',' );
    $csv .= "\n";
    foreach($table_body as $row) {
        $csv .= implode($row, ',' );
        $csv .= "\n";
    }

    $filename = 'table.csv';
    header( 'Content-Type: text/csv' );
    header( 'Content-Disposition: attachment; filename="' . $filename .'"' );
    header( 'Pragma: no-cache' );
    header( "Expires: Sat, 26 Jul 1997 05:00:00 GMT" );

    echo "xEFxBBxBF"; // UTF-8 BOM
    echo $csv;
    exit;
}

global $wpdb;
?>
<h1>Export</h1>

<a href="/export?export=table">Export</a>