How to export CSV table file with PHP

$ret = '';
$arrs = array(array(1,'test1'),
 array(2,'test2'),
 array(3,'test3') ,
 array(4,'test4'),
 array(5,'test5'),
 array(6,'test6'),
 array(7,'test7')
 );
foreach($arrs as $ k=>$arr){
 $ret .= $arr[0].",".$arr[1]." n";
}
//$ret = @mb_convert_encoding ($ret, 'GBK' ,'UTF-8');
header("Content-Disposition: attachment; filename=xxxx.csv");
header("Content-Type:APPLICATION/OCTET-STREAM");
echo $ret;

Note: The above code for exporting csv files using PHP still uses the PHP header function. I hope you can learn from it.