I have been editing the wp_list_pages function in my WordPress installation, via help from this thread: http://wordpress.org/support/topic/85901?replies=5
Without taking away from that thread, I wanted to ask a question spurred from the last entry related to replacement plugins.
I've seen it mentioned that there are plugins to help you customize WordPress functions, and assist in making your own (I'm assuming that if you make your own, they won't be affected by an upgrade of WordPress).
What is this all about, and how does it work? I can modify the code a function outputs adequately most times, but am not familiar with writing my own functions. I don't quite understand how these plugins work.
My goal is to modify the code output by the wp_list_pages function (and associated CSS) and not have it affected by an upgrade.