Full HTTP Request from cURL in PHP

Question

I'm trying to upload an image to a site via their API by trying to mimic a web form and posting the data using cURL. I'm looking to check what cURL is actually sending to the destination site, to ensure I've built the request correctly. I see you can use CURLOPT_VERBOSE to see what it's sending in the request header, but I'm looking to see the posted data, after

Content-Type: multipart/form-data; boundary=----------------------------91f22eea64e8

The data I'm posting is in $post and the request is

        $ch = curl_init();
        $opts = array(
            CURLOPT_POST => 1,
            CURLOPT_CONNECTTIMEOUT => 10,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT => 60,
            CURLOPT_USERAGENT => 'Mozilla/4.0 (compatible;)',
            CURLOPT_POSTFIELDS => $post,
            CURLOPT_URL => 'https://example.com/api',
            CURLOPT_HTTPHEADER => array('Expect:'),
            CURLOPT_VERBOSE => 1
        );
        curl_setopt_array($ch, $opts);
        $response = curl_exec($ch);

Thanks

Can you just sniff the traffic using tcpflow? (sudo tcpflow -c -i eth0 host foobar.com). Replace eth0 with en0 on a Mac; en1 for wifi, etc. — Paul Schreiber
– Paul Schreiber, Commented Dec 7, 2010 at 17:01
Thanks for that Paul. I tried doing something similar with dumcap and saving the data in a file, but it was illegible, think it was in binary. I tried your suggestion with tcpflow and got a similar outcome unfortunately. — eclipse31
– eclipse31, Commented Dec 8, 2010 at 10:00

Rogus · Accepted Answer · 2010-12-07 17:11:41Z

3

I have handled this problem in the past by sending the curl data to myself first, to make sure I am sending the right stuff. The file on my own webserver that I would send to (most likely the very same webserver I am sending from to begin with) needs only this in a .php file: <?php echo file_get_contents('php://input'); ?> so set the URL to that file for your CURLOPT_URL in your current php script, then send it with echo $response; in your curl calling code to see what was sent.

See also: http://www.codediesel.com/php/reading-raw-post-data-in-php/ and http://php.net/manual/en/wrappers.php.php for extra details/examples.

Oh, although in re-reading your question I see that you are sending an image, so you have to send multipart/form-data and that doesn't work with the php://input stream, you have to use php://stdin for that, according to the PHP docs linked above. I expect it will work the same regardless.

edited Dec 7, 2010 at 17:11

answered Dec 7, 2010 at 17:04

Rogus

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3 Comments

eclipse31 Over a year ago

Thanks for this Chris. I had high hopes for your solution, as it's a good idea, but unfortunately couldn't get it to work. Even doing a simple post and echoing file_get_contents('php://input') was returning no data. The best I could do was echoing a print_r($_POST,1). I even tried setting always_populate_raw_post_data in my php.ini (not forgetting to restart Apache) and doing a print_r($HTTP_RAW_POST_DATA,1) but no joy there either.

Rogus Over a year ago

I tested it myself now, and while it does work fine with php://input when submitting regular x-www-form-urlencoded data via post, with multipart/form-data, nothing comes out via php://input or php://stdin. Yeah, I wish I knew what to do about that except to say that I doubt you really want to see the base64 encoded data for your image file anyway, so I still recommend my original solution and just submit all the fields except the uploaded files, and with curl, that should automatically leave out multipart/form-data so you can see everything else properly submitted.

Rogus Over a year ago

Oh, my apologies, you need to turn $post into a string, the associative array form is always sent as multipart/form-data with cURL in PHP (php.net/manual/en/function.curl-setopt.php @ CURLOPT_POSTFIELDS), so use this instead: CURLOPT_POSTFIELDS => http_build_query($post) and that will send the data, minus the base64'd data of the binary files (images) you are transferring.

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