This hook can be used for performing post output tasks. One of the things that you could use this for, is for reading in buffered output using ob_get_contents() in case you started buffering using ob_start() from the ??? hook.

Call time:

After sending the page footer template.

Hook input:

No input.

Hook output:

No output.

Example code:

function phorum_mod_foo_end_output()
{
    // Some made up call to some fake statistics package.
    include("/usr/share/lib/footracker.php");
    footracker_register_request();
}