Apache Logs
This has happened to me a couple times, still more than I would like to admit. First off, I used to have my apache logs named the same as the website URL (“bodhidevelopment.com”). This is a pretty minor problem and can go unnoticed for years… until your server runs out of storage space. Apache2 has a nice little feature to rotate logs, but the default will only look for files with the “.log” extension. I used to regularly have log files that were over a gigabyte, and I could only imagine what kind of performance issues that might cause.
I never really paid attention to PHP warnings/errors unless they were causing serious problems, but it felt like the next logical step after getting the logs in order. A large potion of warnings were just undefined variables being used, which is extremely easy to fix, and can add up fast if there are a large number of variables/loops on a page. This gave me the opportunity to look through code that hasn’t been touched for years.