(I'm pretty new to this, so excuse ignorance of the codebase or terminology)
What I would like to do is have a button (or maybe just a link if necessary) on a page. When the button gets clicked, some stuff happens - a system variable is set, a value gets inserted to an sql table, or the content of the page changes based. Trouble is, I have no idea how to coordinate button-clicks with PHP behavior. I've been trying to figure out the 'sort' button on "memberlist.php", as it seems to do the least amount of work, and I can sorta trace its functions, but not all that well.
If someone could point me to some further resources, or explain how something like this would work, that would be great. Thanks!