how to export meta value in wordpress admin

I need export data of custom post type to file csv in wordpress admin but I has given file csv with header and footer not pure data.

here my code

`
add_action( ‘admin_menu’,’register_export_csv_menu’ );
function register_export_csv_menu()
{

add_menu_page( ‘Export dữ liệu’, ‘Export dữ liệu’, ‘manage_options’, __FILE__, ‘export_frm’, ”, 120);
}
function export_frm()
{
global $wpdb;

$sql_register_events=”select m.meta_value as ho_ten ” ;
$sql_register_events .=”,m1.meta_value as dien_thoai “;
$sql_register_events .=” ,m2.meta_value as email ” ;
$sql_register_events .=”,m3.meta_value as su_kien_thang ” ;
$sql_register_events .=”,p.post_date as ngay_dang_ky “;
$sql_register_events .= ” from wp_postmeta m “;
$sql_register_events .= “inner join wp_posts p on m.post_id=p.id and m.meta_key=’ho_ten’ “;
$sql_register_events .= “inner join wp_postmeta m1 on m1.post_id=p.id and m1.meta_key=’dien_thoai’ ” ;
$sql_register_events .= “inner join wp_postmeta m2 on m2.post_id=p.id and m2.meta_key=’email’ “;
$sql_register_events .= “inner join wp_postmeta m3 on m3.post_id=p.id and m3.meta_key=’su_kien_thang’ ” ;
$sql_register_events .= “where p.post_type=’register_events’ “;

//$results=$wpdb->get_results($sql_register_events,ARRAY_A);
$results=$wpdb->get_results($sql_register_events);

header(‘Content-Encoding: UTF-8’);
header(‘Content-type: text/csv; charset=UTF-8’);
header(“Content-type: application/vnd.ms-excel”);
header(“Content-Disposition:attachment;filename=register_events.csv”);
header(‘Pragma: no-cache’);
echo “\xEF\xBB\xBF”;
ob_start();

$f = fopen(‘php://output’, ‘w’) or show_error(“Can’t open php://output”);

$skt=array(‘Ho_ten’,’Dien_thoai’,’Email’,’Su_kien_thang’,’Ngay_dang_ky’);

fputcsv($f,$skt);
foreach ($results as $rs)
{
$rs_array=(array)$rs;
fputcsv($f, $rs_array);
}
fclose($f);

$csvStr = ob_get_contents();
ob_end_clean();

echo $csvStr;

exit;
}