[PHP] Stupid Cookie Question

[nate]

Sorry for having to ask this because i'm sure its a really simple answer...

I set a cookie with the following...

<?php 
header("Location:  index.php");
SetCookie("password","$password");
SetCookie("cwname","$cwname"); 
?>

User see's a form with username and password fields. It sets whatever he inputs to 
cookies. Now i'm trying to figure out how to delete them! I know you can delete it if 
you set a negative time but I never set a time to it in the first place.

Thanks,
Nate