Undefined scope after ldap search PHP

I want to receive through LDAP the user's givenname.

I am using the following code:

$ldap = ldap_connect("ldap://domain.com");
        ldap_set_option($ldap, LDAP_OPT_PROTOCOL_VERSION, 3);
        ldap_set_option($ldap, LDAP_OPT_REFERRALS, 0);
        if ($bind = ldap_bind($ldap, $myusername, $mypassword)) 
        {
            $_SESSION['login_user'] = $myusername;
            $filter = "(sAMAccountName={$myusername})";
            $ldap_dn = "dc=domain, dc=com";
            $attr = array("givenname");
            $result = ldap_search($ldap, $ldap_dn, $filter, $attr) or exit("Unable to search LDAP server");
            $entries = ldap_get_entries($ldap, $result);
            $givenname = $entries[0]['givenname'][0];
            ldap_unbind($ldap);

            setcookie("name", $givenname, time() + (86400 * 30), "/");  

            setcookie("sessao", $local, time() + (86400 * 30), "/"); // 86400 = 1 dia
            //header("location: welcome.php");

        } 

Whenever I login, in the welcome page, the cookie "name" is empty, so I removed the redirect to see what is happening.

Now I am receiving the following error:

Notice: Undefined offset: 0 in C:\wamp\www\OperPHP\authentication.php on line 21

Observation: Line 21 is:

$givenname = $entries[0]['givenname'][0];

I guess is something in my LDAP query, but I don't know where it could be.

Anyone could help?