* PHP's `create_function` will create lambda functions in runtime, so you don't have to worry about external files. It'll take the parameter list and the internal code, respectively, and return the newly added function name, which will serve here as callbacks.
* Indexing these items as `onBeginRequest` and `onEndRequest` will trigger attaching callbacks to application events.
* Event handlers are even acceptable since they'll take the event object as first argument.
[...]
* If the current browser is not capable of uncompressing gzip, gzhandler will leave the output untouched.
(If you need additional functionality, you may want to create a separate file for these functions.)