I remember Matt’s Scripts Archive as an absolute gold mine for learning how to make web applications through example in the pre-PHP days, which was pretty challenging when all you had to work with is CGI and maybe SSI if your hosting provider was particularly advanced. It’s what got me started as a web application developer 30+ years ago. I guess I probably learned about security the hard way by following his example…
This is the big thing for me as well. Just having a source for code to show me how to do certain things was absolutely huge. I don't think I even used his code as-is hardly at all. It was part of the View Source way a lot of us learned to code.