Can I fork a PHP thread?

There are occasions when I'd like to execute some long-running task in the background, in response to some user action. It seems that PHP has all the neccesary mechanisms to allow me to do this, but in my perusing of the manuals/FAQ's/digests, etc, I don't see such a facility. For example, I'd like to do something like this: function long_running_background_task() { ... } function handle_some_action() { ... fork (long_running_background_task); } In the cases I'd like to do this, I can manage synchronization externally... (i.e., implement join by waiting for a /tmp file to appear or something), so I'm not asking for a join, or any sychronization facilities. Does anyone agree that this would be useful? Is there another way to accomplish this? Better yet, does this function already exist, but has managed to hide for all this time...? thanks, dylan