My then-teenage son came up with the idea to create an app that allowed the user to find people in the area for pick-up soccer games. I expanded the idea to all popular sports, games, and activities.
I coded the app itself in PHP, though the site is in WordPress. The app took about 10,000 lines of code. It registered the user, took an inventory of the activities they would be interested in, assessed which areas they were willing to travel to for activities. Then, when a user proposed a particular event, the system emailed everyone in their area that also expressed interest in the activity. Those notified could then commit to attend.
The data gathered during registration was saved to a MySQL database. Then that same data was retrieved for use to find other users in the area that were interested in the same activities when one was scheduled.
After performing market research through polls, I identified the best price to charge ($9.99/month) and launched the site via tweets and Facebook. Sadly, the idea did not take off. However, this project definitely stretched my coding prowess with PHP.