如何使用PHP中的GSS-API机制从Windows执行LDAP SASL绑定到Active Directory？

I have an Active Directory server and a Windows WAMP server hosting PHP web applications that need to be able to authenticate to Active Directory using Kerberos.

I was able to easily connect and bind to the Active Directory host using some sample PHP code, but I'm not sure how to do so with Kerberos. I have see many forums and blogs detailing how to do this on *NIX machines, but that doesn't help me with my situation.

I did use Wireshark and Fiddler to confirm that there is no Kerberos or NTLM negotiating happening.

Sample code I used to connect and bind to LDAP:

<?php   
   $ldaphost = "example.domain.com";
   $ldapport = 389;
   $ldapuser = "user";
   $ldappass = "password";

    $ldapconn = ldap_connect( $ldaphost, $ldapport )
    or die( "Unable to connect to the LDAP server {$ldaphost}" );

    if ($ldapconn)
    {
        $ldapbind = ldap_bind($ldapconn, $ldapuser, $ldappass);

        if ($ldapbind)
        {
            echo "LDAP connection successful";
        }
        else
        {
            echo "LDAP connction failed";
        }
    }
?>

Any help will be greatly appreciated, thanks!

Update: I've been wrestling with this all day and I think I need to use ldap_sasl_bind(), possibly using GSSAPI as the mechanism... No matter what parameters I put in to ldap_sasl_bind(), I get the following error: 'Unable to bind to server: Unknown authentication method'

I'm not sure how to implement GSSAPI, but some examples I've seen show using ldap_start_tls(), but I keep getting a 'Unable to start TLS: Server is unavailable' error.

I don't know if anyone knows anything about ldap_sasl_bind() (which is undocumented by PHP) or ldap_start_tls, but if this is the way I should be going, please point me in the right direction.