PHP cURL: curl_exec to a webform that redirects

Question

I'm new to cURL and I am having a bit of an issue getting it to work. I need to send some parameters, as well as upload a file to a webform. The webform in question will take the file and the input parameters and convert the file to another format. When using this webform directly, submit redirects to a new page that displays a progress bar showing the progress of the file conversion. On completion a download link appears.

What I need to do is submit a file (with parameters), wait for the conversion to complete, download the file and proceed with my PHP code that processes the downloaded file. However, I'm having a hard time with cURL and I'm not sure if it has something to do with the redirect to the page with the progress bar that occurs. Example code is below:

$full_file_path = realpath($inputfile);
$data = array('param1' => '1', 'param2' => '2', 'file' => '@'.$full_file_path);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://example.com/Converter/index.pl');
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$response = curl_exec($ch);
curl_close($ch);

#get converted file

$file_head=substr($inputfile, 0, strpos($inputfile, '.raw'));
$output_file=$file_head.".mzXML";
$url="http://example.com/Converter/temp/".$output_file;
$fp = fopen ($output_file, 'w+');

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_FILE, $fp);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
$response = curl_exec($ch);
curl_close($ch);

The initial instance of $response returns the empty webform. I get no errors with curl_error and from curl_getinfo I can see that I am correctly connecting to the server, however the file conversion process should take ~5minutes while the curl process completes in <1 sec. I'm not sure what's going wrong or how to get more info to tell me what's happening. My best guess is it has something to do with the redirect but I don't know for sure.

Any help is much appreciated.

EDIT

Here is the output from CURLOPT_VERBOSE

• Adding handle: conn: 0x7fa754818000
• Adding handle: send: 0
• Adding handle: recv: 0
• Curl_addHandleToPipeline: length: 1
• Conn 16 (0x7fa754818000) send_pipe: 1, recv_pipe: 0
• About to connect() to example.com port 80 (#16)
• Trying XX.XXX.XXX.XXX...
• Connected to example.com (XX.XXX.XXX.XXX) port 80 (#16)
• POST /Converter/index.pl HTTP/1.1
• Host: example.com
• Accept: /
• Content-Length: 249010577
• Expect: 100-continue

• Content-Type: multipart/form-data; boundary=----------------------------52f3c644b6de

• HTTP/1.1 100 Continue

• HTTP/1.1 200 OK
• Date: Fri, 01 May 2015 14:01:17 GMT
• Server Apache/2.2.22 (Win32) is not blacklisted
• Server: Apache/2.2.22 (Win32)
• Transfer-Encoding: chunked

• Content-Type: text/html; charset=ISO-8859-1

• Connection #16 to host example.com left intact

Answer 1

I guess you can use header() to redirect the user to the converted file, also, remove the last curl, and use CURLOPT_FOLLOWLOCATION, true on the first curl ie:

$full_file_path = realpath($inputfile);
$data = array('param1' => '1', 'param2' => '2', 'file' => '@'.$full_file_path);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://example.com/Converter/index.pl');
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$response = curl_exec($ch);
curl_close($ch);

#get converted file

$file_head=substr($inputfile, 0, strpos($inputfile, '.raw'));
$output_file=$file_head.".mzXML";
$url="http://example.com/Converter/temp/".$output_file;
$fp = fopen ($output_file, 'w+');

header("Location: $url");