Tracking Users Using WML

Reading Cookies with Perl

Reading cookies with Perl is even easier than setting them, thanks to the environment variable HTTP_COOKIE. This variable contains name/value pairs for all applicable cookies (those matching the current scope).

To parse the name/value list, you could use the following code:

@nvpairs=split(/[,;] */, $ENV{'HTTP_COOKIE'});
foreach $pair (@nvpairs) {
   ($name, $value) = split(/=/, $pair);
   $cookie{$name} = $value;
}

This code effectively parses the cookie list into the array $cookie, where each value can be accessed by its name. For example, our earlier "name" example would yield:

$cookie{'name'} = "Steve"

An extended example, displaying the cookie value in WML, is shown below:

#!/usr/bin/perl

# Break cookies into name/value pairs
# and store into cookie array
@nvpairs=split(/[,;] */, $ENV{'HTTP_COOKIE'});
foreach $pair (@nvpairs) {
   ($name, $value) = split(/=/, $pair);
   $cookie{$name} = $value;
}

# Define WML deck
$deck = '
<wml>
  <card>
    <p>
      Cookie (name) = '
.$cookie{'name'}.'
    </p>
  </card>
</wml>';

# Send Content-type and Set-Cookie headers
print "Content-type: text/vnd.wap.wml \n";
print "Set-Cookie: name=Steve; expires=$date; \n";

# Send WML headers
print "\n<?xml version=\"1.0\"?>\n";
print "<!DOCTYPE wml PUBLIC \"-//WAPFORUM//DTD WML 1.1//EN\""
   . " \"http://www.wapforum.org/DTD/wml_1.1.xml\">\n";

# Send the deck
print $deck;

If the cookie was still set, this code would display the following:

Cookie (name) = Steve

Deleting Cookies

To remove a cookie, you simply set the expiration of the cookie to a date/time that has already passed. For example, we could use the code earlier but subtract a day or two to expire the cookie. The code, using Date::Calc functions, would resemble the following:

# Get today in GMT
($year,$month,$day) = Today([$gmt]);
# Subtract a year (365 days)
($year,$month,$day) =
  Add_Delta_Days($year,$month,$day,"-365");
# Get textual representations of month and day of week
$dow =  Day_of_Week_to_Text(Day_of_Week($year,$month,$day));
$month = Month_to_Text($month);
# Make sure day is two digits
if ($day<10){
 $day = '0'.$day;
}
# Assemble expiration date
$date = $dow.", ".$day."-".$month."-".$year." 23:59:59 GMT";

Note the use of a minus sign in the Add_Delta_Days function to subtract a year from today. We could just as easily subtract only one day.