Launch an X Windows app from Apache (PHP or Perl)

["elentirmo@gmail.com" <elentirmo@gmail.com>]

Hi
I'm setting up an automated movie player system on my Ubuntu box and
what I want to be able to do is run an application (totem) when a I
click a link to a movie on my page. This will be run from the server,
logged in as my default account (it'll be a home theatre system)
The php command I'm calling is
$command=@system("/usr/bin/totem --fullscreen /mnt/hdd1/MOVIE");
Now because www-data is actually calling this command I get the error
(totem:9414): Gtk-WARNING **: cannot open display:
in the apache logs.
I've tried adding www-data to sudoers, to the root group etc but no
dice. I believe it's soemthing to do with the DISPLAY environment
variable but I'm not sure how to change this or what to change it to to
enable this to work.
Others have suggested freevo or writing the app as perl+GTK but I want
to do it from PHP/Perl if at all possible
many thanks in advance for any help

cheers

Lucas