How to authenticate users in PHP using Active Directory without username and password. When a domain user login, it can also logged in PHP application which is connected with Active Directory.
What you are looking for is seamless kerberos SSO authentication using active directory where a browser automatically sends some negotiation token that you need to verify. Usually, this is delegated to the web server. There are several Apache plugins to do so:
mod_auth_sspi for Apache on Windows: http://mod-auth-sspi.sourceforge.net/
mod_auth_kerb for Apache on Linux: http://modauthkerb.sourceforge.net
mod_ntlm for Apache on Linux: http://modntlm.sourceforge.net
mod_auth_ntlm_winbind for Apache http://adldap.sourceforge.net/wiki/doku.php?id=mod_auth_ntlm_winbind