help with popup field

how do I go about putting a popup field

say it like this the nick come back empty so if it does I want user to put in a nick next to Guest_ by using a popup


if ($nickname=="") {
$nickname = "Guest_";
}

As in a little alert box that says a message? if so that's Javascript.

like if the nick null a box popup then u put a nick in

other thing I can think of is adding randoms numbers how would I do that ?


if ($nickname=="") {
$nickname = "Guest_(.Rand 100/100000)";
}

if (empty($nickname))
{
$nickname = 'Guest_' . rand(100, 100000);
}

Although you'd probably be better off pulling off of time.

As for a popup, as mentioned that is not PHP, its client side technology like Javascript.

Thank you :)