PHP - Using CURL to authenticate and download a remote File

Question

I'm trying to use php to post variables to another php on a remote server and on the file at the remote server I want to read the file and force its download. The file on the remote server is not on a public folder, that's why I need to call the file first, so it authenticates and get the protected file.

Everything works, but I don't get any file back.

At the remote PHP I'm using standards readfile and headers to download a file.

I think maybe the problem is with the CURL setup, I'm using the standard CURL calls is there any specific header or setup I need to use when I call CURL to have the file downloaded?

This is the CURL i'm using

$request = curl_init();
curl_setopt($request, CURLOPT_URL, $postURL);
curl_setopt($request, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($request, CURLOPT_VERBOSE, 0);
curl_setopt($request, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($request, CURLOPT_POST, 1);
curl_setopt($request, CURLOPT_POSTFIELDS, $postFields);
curl_setopt($request, CURLOPT_RETURNTRANSFER, 1);

$response = curl_exec($request);
curl_close($request);

Where $postFields contain the variables to authenticate and confirm the file on the other server.

On the other server the php after authenticating does the normal force download:

header('Content-Description: File Transfer');
header('Content-Disposition: attachment; filename="'.$newFileName.'"');
header('Content-Type: application/octet-stream');
header('Content-Transfer-Encoding: binary');
header('Content-Length: ' . filesize($path));
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Expires: 0');

readfile($path);

Thanks!

EDIT: Hi, I believe I found the issue. The problem is that when I call through .$post on the jquery the local server php, the curl interrupts the ajax call

        $.post('local.php', $(this).serialize(), function(data){
            alert(data);
            }
        }, "json").fail(function() {
            alert('error');
        });

So I'll have to figure it out how to call through the jquery the local.php without breaking the process. Thanks for your help!

Please add the relevant code you already have got (especially the curl initialization, even if it is not working). That way we can get a better understanding of what you want to achieve / where the problem is. — dhh
@Kitara, how are you getting $newFileName and $path variables? If you put a print_r($response), what is the output? — Dimas Pante
Hi @DimasPante $newFileName is just a arbitrary name with the extension of the real file. And $path is the path to the file we want to be downloaded. I already put an output of php errors and php finds the file, the path is not the issue. — Kitara

dhh dhh · Accepted Answer · 2015-06-18T05:05:08

Assuming you are using basic HTTP authentication on the target site - you can add logon information by using the option CURLOPT_USERPWD.

curl_setopt($request, CURLOPT_USERPWD, "$username:$password");

edit: regarding the ajax call - jQuery will execute the fail method, if the server returns an error. Furthermore - you are specifying json as data-type in your ajax-call. The download will not return json, I think.

edit 2: I do not think that a download via $.post will be possible that way, as jQuery only knows one of xml, html, script, json, jsonp, text. You might try authenticating via your ajax request, have the ajax response return the download URL redirect the browser to that target. Or you could try using a hidden iframe for that download. Have a look at those posts (here and here) - the issue is discussed in details here.

PHP - Using CURL to authenticate and download a remote File

1 Answers