debugging php webapps

Hi.

Looking over different articles.. Figured I'd post here as well.

What tools are used to debug webapps/php apps?

Treat the user/reader as a 6 year old!

What setups, what tools, what sites have you found that detail the "tricks"

I'm looking at firing up some bootstrap/laravel webapps, and I'm going to
want to get to the level of understanding "as fast as possible" regarding
front-side/serverside interaction, and/or bootstrap integration to laravel.

thanks much!