PHP cURL not returning Content-Encoding header

Question

When I run curl -I http://api.stackoverflow.com/1.1/badges fro my terminal, it shows me the following headers:

HTTP/1.1 200 OK
Cache-Control: private
Content-Length: 42804
Content-Type: application/json; charset=utf-8
Content-Encoding: gzip
X-AspNetMvc-Version: 4.0
X-RateLimit-Max: 300
X-RateLimit-Current: 297
X-AspNet-Version: 4.0.30319
Set-Cookie: .ASPXBrowserOverride=; expires=Mon, 08-Oct-2012 04:29:28 GMT; path=/
Date: Tue, 09 Oct 2012 04:29:27 GMT

Yet, when I run the same cURL request through PHP, I get this:

Array
(
    [url] => http://api.stackoverflow.com/1.1/badges?10102
    [content_type] => application/json; charset=utf-8
    [http_code] => 200
    [header_size] => 277
    [request_size] => 85
    [filetime] => -1
    [ssl_verify_result] => 0
    [redirect_count] => 0
    [total_time] => 0.168343
    [namelookup_time] => 0.023417
    [connect_time] => 0.046293
    [pretransfer_time] => 0.046365
    [size_upload] => 0
    [size_download] => 42804
    [speed_download] => 254266
    [speed_upload] => 0
    [download_content_length] => 42804
    [upload_content_length] => 0
    [starttransfer_time] => 0.097563
    [redirect_time] => 0
    [certinfo] => Array
        (
        )

    [redirect_url] => 
)

The major difference that matters to me is that when run through PHP, I do not get the Content-Encoding header, without which I do not know if the content needs to be gzip inflated or not.

Is there a way to get the Content-Encoding header, or to check for gzip compression some other way?

Alain · Accepted Answer · 2012-10-09 05:56:06Z

There is no header_response nor accept-encoding in the returned getinfo array. I thought CURLINFO_HEADER_OUT on getinfo would give response headers, but only request headers are given.

But you can get raw headers using the CURLOPT_HEADER option set to true. So I suggest you to do something less natural :

$curl = curl_init();

$opts = array (
        CURLOPT_URL => 'http://api.stackoverflow.com/1.1/badges',
        CURLOPT_TIMEOUT => 120,
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_FOLLOWLOCATION => true,
        CURLOPT_ENCODING => 'gzip',
        CURLOPT_HEADER => true,
);
curl_setopt_array($curl, $opts);

$return = curl_exec($curl);

list($rawHeader, $response) = explode("\r\n\r\n", $return, 2);

$cutHeaders = explode("\r\n", $rawHeader);
$headers = array();
foreach ($cutHeaders as $row)
{
    $cutRow = explode(":", $row, 2);
    $headers[$cutRow[0]] = trim($cutRow[1]);
}

echo $headers['Content-Encoding']; // gzip

vstm · Accepted Answer · 2012-10-09 05:32:34Z

If you set CURLOPT_HEADER to true, curl returns the header alongside the body. If you're just interested in the header, you can set CURLOPT_NOBODY to true and the body is not returned (which emulates the -I flag on the command line).

This example sets just the CURLOPT_HEADER, reads the Content-Encoding header (if it is set) and uncompresses the body:

$curl = curl_init();

curl_setopt($curl, CURLOPT_URL, "http://api.stackoverflow.com/1.1/badges");
curl_setopt($curl, CURLOPT_HEADER, 1);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);

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

list($header, $body) = explode("\r\n\r\n", $response, 2);
if(preg_match('@Content-Encoding:\s+(\w+)@i', $header, $match)) {
    switch (strtolower($match[1])) {
        case 'gzip':
            $body = gzdecode($body);
        break;

        case 'compress':
            $body = gzuncompress($body);
        break;

        case 'deflate':
            $body = gzdeflate($body);
        break;
    }
}
echo $header;
echo $body;

Disclaimer: gzdecode might not be available in your PHP-version. I've tested it with PHP 5.4.4 and it worked.

You could also install the HTTP_Request2-PEAR package which does that for you (plus you get easy access to the headers without HTTP-header parsing):

include 'HTTP/Request2.php';
$request  = new HTTP_Request2('http://api.stackoverflow.com/1.1/badges',
    HTTP_Request2::METHOD_GET);

$response = $request->send();

echo $response->getBody();

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