Over the past months I've learnt a lot about Apache, PHP and MySQL in my spare time as I wanted to implement a database application with a web front end for my own purposes. While the effort would have probably been too high just for this, I was additionally motivated by the fact that learning about these tools also gives me a deeper understanding of how web based services work under the hood.
Databases have always been my weak point as I had little use for them so far. After my project I have gained a much better understanding about MySQL and SQLite and feel comfortable working with them. What a nice side effect.
And in addition, the knowledge gained helps me to better understand, debug and fix issues of open source web based applications I am using on a regular basis. A practical example is Selfoss, my RSS aggregator of choice I've been using ever since Google decided to shut down their RSS reader product last year. While I am more than happy with it, the feed update procedure stops working every couple of months for a while. When it happened again recently I dug a bit deeper with the knowledge I have gained and found out that the root cause were links to non-existing web pages that the update process tried to use. Failing to load these pages resulted in an abort of the update process. A few lines of code and the issue was fixed.
I guess it's time to learn about 'git' now so I can not only fix the issue locally and report it to the developer but also supply a fix for it and potentially further features I'm developing for it. Open source at its best!