У меня работало вот так:
define( 'AD_SERVER_IP', '192.168.7.99' );
define( 'AD_DOMAIN', 'domain' );
$adServer = "ldap://".AD_SERVER_IP;
$ldap = ldap_connect($adServer);
$username = 'username';
$password = 'password';
$ldaprdn = AD_DOMAIN . "\\" . $username;
ldap_set_option($ldap, LDAP_OPT_PROTOCOL_VERSION, 3);
ldap_set_option($ldap, LDAP_OPT_REFERRALS, 0);
ldap_set_option($ldap, LDAP_OPT_SIZELIMIT, 3);
$bind = @ldap_bind($ldap, $ldaprdn, $password);
if($bind){
$filter="(sAMAccountName=$username)";
$params = array('cn','telephonenumber');
$result = ldap_search($ldap,"dc=".AD_DOMAIN.",dc=local",$filter,$params );
$info = ldap_get_entries($ldap, $result);
@ldap_close($ldap);
}