Write to PHP output buffer and then download CSV from buffer

Question

I need to write a CSV file to the PHP output buffer and then download that file to the client's computer after it's done writing. (I wanted to just write it on the server and download it which was working, but it turns out I won't have write access on production servers).

I have the following PHP script:

$basic_info = fopen("php://output", 'w');
$basic_header = array(HEADER_ITEMS_IN_HERE);

@fputcsv($basic_info, $basic_header);

while($user_row = $get_users_stmt->fetch(PDO::FETCH_ASSOC)) {
    @fputcsv($basic_info, $user_row);
}

@fclose($basic_info);

header('Content-Description: File Transfer');
header('Content-Type: application/csv');
header('Content-Disposition: attachment; filename=test.csv');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize("php://output"));
ob_clean();
flush();
readfile("php://output");

I'm not sure what to do. The CSV file downloads but displays nothing. I assume it has something to do with the ordering of my ob_clean() and flush() commands, but I'm not sure what's the best way to order these things.

Any help is appreciated.

Answer 1

You're doing a little too much. Create the script with the sole purpose of outputting the CSV. Just print it out directly to the screen. Don't worry about headers or buffers or php://output or anything like that yet.

Once you've confirmed that you're printing the data out to the screen appropriately, just add these headers at the beginning:

<?php
header("Content-disposition: attachment; filename=test.csv");
header("Content-Type: text/csv");
?>

... confirm that that downloads the file appropriately. Then you can add the other headers if you like (the headers I included above are those I've used myself without any extra cruft to get this working, the others are basically for efficiency and cache control, some of which may already be handled appropriately by your server, and may or may not be important for your particular application).

If you want, use output buffering with ob_start() and ob_get_clean() to get the output contents into a string which you can then use to fill out Content-Length.