I am trying to rename group using PHP but i am getting error **Naming voilation**

Following is my code which successfully connects to LDAP server.
Everything is working fine just need to know how fix this error.

```
$ldap = ldap_connect("my_ldap_host");
if ($ldap) {

    $bind_rdn = "my_bind_rdn";
    $bind_password = "my_bind_password";
    $is_binded = ldap_bind($ldap, $bind_rdn, $bind_password);
    if($is_binded) {

        $ldap_ou = "my_ou";
        $ldap_base_dn = "my_base_dn";

        $group_entry = array();
        $group_entry["cn"] = $group_new_name;
        $group_dn = "cn=" . $group_old_name . ",ou=" . $ldap_ou . "," . $ldap_base_dn;
        $is_modified = ldap_modify($ldap, $group_dn, $group_entry);
        if($is_modified) {
            echo "Success";
        }
        else {
            echo "Fail : " . ldap_err($ldap);
            // here getting error Naming voilation
        }
    }
    else {
        echo "Binding failed";
    }
}
else {
    echo "Fail to connect to LDAP server";
}

```