PHP: PDO + CSV export not downloading (headers issue?) - php

Question

I'm having a hard time making my CSV export function work.
I've found around plenty of examples using mysqli_* functions, but I'm actually using PDOs so I had to adapt some questions/answers to my needs.
From what I can see, I'm properly parsing and writing data to the *.csv file, but at the end I don't simply get any "Download" modal from the browser.
Again, looking around, I've understood I may have some kind of problem with my headers, so I'm asking for your help.
This is my PHP function snippet:
function downloadAsCSV($dsn, $dbUser, $dbPsw, $options) {
// New PDO connection.
$pdo = pdoConnect($dsn, $dbUser, $dbPsw, $options);
$query = ... // Not going to write it down.
// Let's query the database, ...
$stmt = $pdo->prepare($query);
// Setting up the query variables here...
[...]
// Executing the statement...
$stmt->execute();
// Headers.
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header('Content-Description: File Transfer');
header("Content-Type: text/csv");
header("Content-Disposition: attachment; filename='export.csv'");
header("Pragma: no-cache");
header("Expires: 0");
// Let's open tbe "*.csv" file where we'll save the results.
$fp = fopen("php://output", "w");
if ($fp) {
$first_row = $stmt->fetch(PDO::FETCH_ASSOC);
$headers = array_keys($first_row);
fputcsv($fp, array_values($first_row));
fputcsv($fp, $headers);
// ... fetch the results...
$workpiecesArray = $stmt->fetchAll();
// ... and, finally, export them.
foreach ($workpiecesArray as $workpiece) {
fputcsv($fp, array_values($workpiece));
}
}
fclose($fp);
// Closing the connection.
$stmt = null;
$pdo = null;
}
function mysqli_field_name($result, $field_offset) {
$properties = mysqli_fetch_field_direct($result, $field_offset);
return is_object($properties) ? $properties->name : null;
}
I've taken inspiration to write the table column titles from this answer.

Answer 1

What you need to do is to print the file, which you're not doing right now.
See this example using readfile:
http://php.net/manual/en/function.header.php#example-5554
Simply put:
1.Replace
$fp = fopen("php://output", "w");
with
$tmpfname = tempnam("/", "");
$fp = fopen($tmpfname, "w");
2.Replace
fclose($fp);
with
fclose($fp);
readfile($tmpfname);
unlink($tmpfname);
and this will work

Answer 2

header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="export.csv"');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize('export.csv'));
readfile($csvFile);
exit;
`put this after` fclose($fp);