Authenticating to webservice with Kerberos from PHP in IIS - php

Question

I am writing a PHP webapplication that has to connect to a webservice using Kerberos 5 authentication (Active Directory). My PHP website is hosted on IIS 7.5 with PHP 5.5. The application pool is running under the account that is authorized in Active Directory and for the target webservice.
I tried every example code that I could find on this site and other sites but to no avail.
This is the PHP code I am using now:
$url = 'http://mywebservice/login/kerberos';
$ch = curl_init();
$options = [
CURLOPT_RETURNTRANSFER => true,
CURLOPT_VERBOSE => true,
CURLOPT_HTTPAUTH => CURLAUTH_GSSNEGOTIATE,
CURLOPT_HTTPHEADER => ['Authorization: Negotiate'],
CURLOPT_RETURNTRANSFER => true,
CURLOPT_USERPWD => 'myuser',
CURLOPT_URL => $url,
CURLOPT_HEADER => 1
];
curl_setopt_array( $ch, $options);
$result = curl_exec($ch);
$header_size = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
$header = substr($result, 0, $header_size);
$body = substr($result, $header_size);
print $result;
This gives me the following message:
HTTP/1.1 302 Found Date: Fri, 21 Oct 2016 14:49:15 GMT X-Robots-Tag: noindex,nofollow WWW-Authenticate: Location: http://mywebservice/login?login_fail Content-Length: 0
When I remove the CURLOPT_HTTPHEADER => ['Authorization: Negotiate'] l get an Internal Server error from the curl module.
When I use curl commandLine I get the following result:
curl --negotiate http://mywebservice/login/kerberos -umyuser#mydomain --verbose -c "c:\cookie.txt" -b "c:\cookie.txt"
Enter host password for user 'myuser#mydomain':
* Trying (192.168.1.1...
* Connected to mywebservice (192.168.1.1) port 80 (#0)
> GET /login/kerberos HTTP/1.1
> User-Agent: curl/7.41.0
> Host: mywebservice
> Accept: */*
> Cookie: JSESSIONID_PUBLIC=X(MASKED)XXXXXXXXXXXXXXXXX
>
< HTTP/1.1 401 Unauthorized
< Date: Fri, 21 Oct 2016 14:52:46 GMT
< X-Robots-Tag: noindex,nofollow
< WWW-Authenticate: Negotiate
< Expires: Thu, 01 Jan 1970 00:00:00 GMT
< Last-Modified: Thu, 20 Oct 2016 14:52:46 GMT
< Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
< Pragma: no-cache
< P3P: CP=CAO PSA OUR
< Content-Type: text/html; charset=UTF-8
< Content-Length: 3643
<
* Ignoring the response-body
* Connection #0 to host mywebservice left intact
* Issue another request to this URL: 'http://mywebservice/login/kerberos'
* Found bundle for host mywebservice: 0xXXXXXXX
* Re-using existing connection! (#0) with host mywebservice
* Connected to mywebservice (192.168.1.1) port 80 (#0)
* Server auth using Negotiate with user 'myuser#mydomain'
> GET /login/kerberos HTTP/1.1
> Authorization: Negotiate X(MASKED)XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXD
w==
> User-Agent: curl/7.41.0
> Host: mywebservice
> Accept: */*
> Cookie: JSESSIONID_PUBLIC=X(MASKED)XXXXXXXXXXXXXXXXX
>
< HTTP/1.1 302 Found
< Date: Fri, 21 Oct 2016 14:52:46 GMT
< X-Robots-Tag: noindex,nofollow
< WWW-Authenticate:
< Location: http://mywebservice/?login_fail
< Content-Length: 0
<
* Connection #0 to host mywebservice left intact
When I test with the KerberosAuthenticationTester tool (http://blog.michelbarneveld.nl/michel/archive/2009/12/05/kerberos-authentication-tester.aspx) it authenticates me right away when I pass the url and credentials.
I assume that it is not working because I am missing the krb5 library. I could not find it as a DLL so I tried recompiling it with the PHP source in Visual Studio. This is not working for me as well, I am missing the config.w32 file. If necessary I can elaborate on that but first I want to know if this is really needed.
I also installed MIT Kerberos but this did not help aswell.
Is it correct that I need the krb5 DLL, or am I on the wrong track? If I need this DLL, where can I get it or how can I compile it? If there is another solution I would be very happy to hear it.
Thanks everyone for taking your time for me and replying!