[evenmonkeys]

You'll have to use plug-ins. Create a custom page and call for the variable in that custom page. For example...

$variable

Now create a plug-in that calls for the php file and defines the variable. You can do this with the following script. Be sure to set it to global_start.

ob_start();
include('hyperlink_to_the_php_file');
$variable = ob_get_contents();
ob_end_clean();

That's how I've done it.