How can I tell php if NT_User Is Not List Display "NONE"?

[d.brandusa]

This is what I use to display the full name of our NT Users:


<?php

//Detect NT User
$nt_logon_user = $_SERVER["LOGON_USER"];

//Strip Server Info, Only Display Username -- Server //// Slashes Are Backwards to Display Code -- Should Be = \\ x 4
$nt_logon_user = str_replace("SERVER////", "", $nt_logon_user);

//Once Detected, Display Full Name
if(strtoupper($nt_logon_user) == USER1) {
$nt_display_name = "User 01";
} elseif(strtoupper($nt_logon_user) == USER2) {
$nt_display_name = "User 02";
} elseif(strtoupper($nt_logon_user) == USER3) {
$nt_display_name = "User 03";
} elseif(strtoupper($nt_logon_user) == NOTHING OR BLANK) {
$nt_display_name = "No User";
}
//etc...
?>


How can I tell the script if there is no USER1, USER2, USER3, etc... detected, to result to "NOTHING OR BLANK" then display "No User";

Is this possible?