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api – How to parse response headers in PHP?

Posted by: admin July 12, 2020 Leave a comment

Questions:

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?

How to&Answers:

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:

It seems that the only header withou a : is the HTTP version and status.
Do an array_shift to extract that, iterate through the others creating an array like so:

$parsedHeaders = array();
foreach ($headers as $header) {
    if (! preg_match('/^([^:]+):(.*)$/', $header, $output)) continue;
    $parsedArray[$output[1]] = $output[2];
}

ps: untested.

— edit —

enjoy 😉

/**
 * Parse a set of HTTP headers
 *
 * @param array The php headers to be parsed
 * @param [string] The name of the header to be retrieved
 * @return A header value if a header is passed;
 *         An array with all the headers otherwise
 */
function parseHeaders(array $headers, $header = null)
{
    $output = array();

    if ('HTTP' === substr($headers[0], 0, 4)) {
        list(, $output['status'], $output['status_text']) = explode(' ', $headers[0]);
        unset($headers[0]);
    }

    foreach ($headers as $v) {
        $h = preg_split('/:\s*/', $v);
        $output[strtolower($h[0])] = $h[1];
    }

    if (null !== $header) {
        if (isset($output[strtolower($header)])) {
            return $output[strtolower($header)];
        }

        return;
    }

    return $output;
}

Answer:

Short answer if you have pecl_http: http://php.net/manual/it/function.explode.php

Slightly longer answer:

$header = "...";
$parsed = array_map(function($x) { return array_map("trim", explode(":", $x, 2)); }, array_filter(array_map("trim", explode("\n", $header))));

Answer:

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.

Answer:

best way without http_parse_headers();

function strHeaders2Hash($r) {
    $o = array();
    $r = substr($r, stripos($r, "\r\n"));
    $r = explode("\r\n", $r);
    foreach ($r as $h) {
        list($v, $val) = explode(": ", $h);
        if ($v == null) continue;
        $o[$v] = $val;
    }
    return $o;
}

Answer:

It looks like you’re using get_headers function, if so, use the second parameter of the this function which replaces the numerical values for the output array keys and replaces them with string keys, check out the manual for get_headers function.

a small example would be:

<?php
    $output = get_headers('http://google.com', 1);
    print_r($output);

will produce something like the following array:

Array
(
    [0] => HTTP/1.0 301 Moved Permanently
    [Location] => http://www.google.com/
    [Content-Type] => Array
        (
            [0] => text/html; charset=UTF-8
            [1] => text/html; charset=ISO-8859-1
        )

    [Date] => Array
        (
            [0] => Tue, 24 Sep 2013 11:57:10 GMT
            [1] => Tue, 24 Sep 2013 11:57:11 GMT
        )

    [Expires] => Array
        (
            [0] => Thu, 24 Oct 2013 11:57:10 GMT
            [1] => -1
        )

    [Cache-Control] => Array
        (
            [0] => public, max-age=2592000
            [1] => private, max-age=0
        )

    [Server] => Array
        (
            [0] => gws
            [1] => gws
        )

    [Content-Length] => 219
    [X-XSS-Protection] => Array
        (
            [0] => 1; mode=block
            [1] => 1; mode=block
        )

    [X-Frame-Options] => Array
        (
            [0] => SAMEORIGIN
            [1] => SAMEORIGIN
        )

    [Alternate-Protocol] => Array
        (
            [0] => 80:quic
            [1] => 80:quic
        )

    [1] => HTTP/1.0 200 OK
    [Set-Cookie] => Array
        (
            [0] => PREF=ID=58c8f706594fae17:FF=0:TM=1380023831:LM=1380023831:S=_ehOnNWODZqIarXn; expires=Thu, 24-Sep-2015 11:57:11 GMT; path=/; domain=.google.com
            [1] => NID=67=L85IlJW5yG4l9Suyf1LwKMUTcVHyGv4u9tuuMlBH4pfT1syOJvspcgRJ9uTde1xLTDhI2QcOG_fuJY3sfhw49mayT5WdMHnGeMyhh3SgFTRYVF0RAtBXXmjyDFzMqPKu; expires=Wed, 26-Mar-2014 11:57:11 GMT; path=/; domain=.google.com; HttpOnly
        )

    [P3P] => CP="This is not a P3P policy! See http://www.google.com/support/accounts/bin/answer.py?hl=en&answer=151657 for more info."
)

Answer:

If you want to be extra-safe, use Symfony HTTP Foundation:

composer require symfony/http-foundation

use Symfony\Component\HttpFoundation\Request;

$request = Request::createFromGlobals();

// retrieves an HTTP request header, with normalized, lowercase keys
$request->headers->get('host');
$request->headers->get('content-type');

If you’d rather not have that dependency, here’s an example that I’ve put together to find out if the Cache-Control header has the no-cache value, for instance:

/**
*  [
*    0 => 'Cache-Control: no-cache, no-store, no-validate',
*    1 => 'User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20100101 Firefox/12.0',
*  ]
*/
$headers = headers_list();

foreach ( $headers as $header_string ) {
     /*
     * Regex Samples:
     * "Foo: Bar"
     * "Foo-Bar: Baz-Bar:1"
     *
     * Matches:
     * "Foo"
     * "Foo-Bar"
     */
    preg_match( '#^.+?(?=:)#', $header_string, $key );

    if ( empty( $key ) ) {
        continue;
    }

    $key   = strtolower( reset( $key ) );
    $value = strtolower( ltrim( strtolower( $header_string ), $key . ':' ) );

    if ( $key == 'cache-control' ) {
        if ( strpos( $value, 'no-cache' ) !== false || strpos( $value, 'no-store' ) !== false ) {
            $nocache = true;
        }
    }
}