Just helped out a friend with a Wordpress website.. Always feels like hacking a big bunch of spaghetti with

add_filter

etc. but in the end it kind of works and Wordpress is quite end-user (or in this case “admin”) modifiable. • What do you think of Wordpress’

add_filter

and

add_hook

system (combined with overridable files) for plugins? • Do you know of apps with a better plugin system? Where plugins can still easily modify both core functionality, and functionality from other plugins? Tips for resources on designing highly modifiable systems?

Emacs: • there is no difference between user configuration and packages • everything is global • everything is overridable • everything is configurable (as that's pretty much the culture evolved around emacs and everyone expects maximum customizability of everything) • hooks to trigger code on events • advice system to partially modify functions TeX: • everything is global and modifiable • also feels like a big bunch of spaghetti

the hook method is how game engines work too, I quite like it, I have adopted it in a few places too. It usually requires your hooks to do side effects, so its not for the FP purists!