If you want to look at what's in the $COOKIE variable, you can use [man]var_dump[/man] or [man]print_r[/man]:
// recursively prints out contents of all cookies available in this script
As for what that ASP code accomplishes, I'm not certain. If you could use it to set the code in ASP and then redirect to your PHP script, you could use the statement above to inspect what is in there. Alternatively, you could visually inspect the cookie file.