How to parse response headers in PHP?

Question

I have made an oauth signed request to a REST API and have the response headers in an array like so:

[0] => HTTP/1.1 200 OK
[1] => Cache-Control: private
[2] => Transfer-Encoding: chunked
[3] => Content-Type: text/html; charset=utf-8
[4] => Content-Location: https://***
[5] => Server: Microsoft-IIS/7.0
[6] => Set-Cookie: ASP.NET_SessionId=***; path=/; HttpOnly
[7] => X-AspNetMvc-Version: 2.0
[8] => oauth_token: ***
[9] => oauth_token_secret: ***
[10] => X-AspNet-Version: 4.0.30319
[11] => X-Powered-By: ASP.NET
[12] => Date: Sat, 15 Sep 2012 02:01:15 GMT

I am trying to figure out how to parse the headers for easy retrieval of items such as the HTTP status code, Content-Location, oauth_token, and oauth_token_secret?

Answer 1

You'll need to iterate the array and check stripos() to find the header you're looking for. In most cases, you then explode() on : (limiting to 2 resultant parts), but the HTTP response code will require you to explode on the spaces.

// Get any header except the HTTP response...
function getResponseHeader($header, $response) {
  foreach ($response as $key => $r) {
     // Match the header name up to ':', compare lower case
     if (stripos($r, $header . ':') === 0) {
        list($headername, $headervalue) = explode(":", $r, 2);
        return trim($headervalue);
     }
  }
}
// example:
echo getResponseHeader("Content-Type");
// text/html; charset=utf-8

// Get the HTTP response code
foreach ($response as $key => $r) {
  if (stripos($r, 'HTTP/') === 0) {
    list(,$code, $status) = explode(' ', $r, 3);
    echo "Code: $code, Status: $status";
    break;
  }
}

Answer 2

I ended up with this solution which uses regex to find all the keys and values in the header combined with some array mutation from https://stackoverflow.com/a/43004994/271351 to get the regex matches into an associative array. This isn't 100% appropriate for the problem asked here since it takes in a string, but joining an array of strings to get a single string would work as a precursor to this. My case had to deal with raw headers, thus this solution.

preg_match_all('/^([^:\n]*): ?(.*)$/m', $header, $headers, PREG_SET_ORDER);
$headers = array_merge(...array_map(function ($set) {
    return array($set[1] => trim($set[2]));
}, $headers));

This yields an associative array of the headers. If the first line of the headers is included as input (e.g. GET / HTTP/1.1), this will ignore it for the output.