Question

I am using PHP (WAMPServer) to receive a form submission, and then CURL to pass the file to another server for processing.

Here is an example to illustrate (not the actual code):

$data = array(
  'file' => '@'.$_FILES['key']['tmp_name']
);

Here’s what I’m using for CURL… and as I was pasting the code I noticed that I still have http_build_query() in my code… so, that must be the problem.

$CURL = curl_init();
curl_setopt($CURL, CURLOPT_URL, $operation['callback']);
$query_string = http_build_query($arguments);
curl_setopt($CURL, CURLOPT_POSTFIELDS, $query_string);
curl_setopt($CURL, CURLOPT_POST, TRUE);
curl_setopt($CURL, CURLOPT_RETURNTRANSFER, TRUE);
$result = curl_exec($CURL);
curl_close($CURL);
return $result;

My problem is that the last server isn’t receiving the file. Instead, the data is passed as a key-value pair.

$_POST contains 'file' => '@c:\wamp\tmp\xyz.tmp'

What I would prefer, is that the files was transferred, and $_FILES has information about it.

Answer 1

Don’t build an http query for the CURLOPT_POSTFIELDS. Curl can directly accept an array of fields and do its own encoding/mangling.

By building your own query, you’re ‘hiding’ the @ that indicates a file upload and CURL will not trigger its upload mechanisms.

In other words, this will fix things:

$data = array(
  'file' => '@'.$_FILES['key']['tmp_name']
);
curl_setopt($CURL, CURLOPT_POSTFIELDS, $data);