Example of connecting and searching AD
$con = ldap_connect('ad.domain.com');
ldap_set_option($con, LDAP_OPT_PROTOCOL_VERSION, 3);
ldap_set_option($con, LDAP_OPT_REFERRALS, 0);
ldap_bind($con, '[email protected]', 'clear password');
ldap_search($con, 'DC=domain,DC=com', '(uniqueMember=user)');