PHP Gas Mileage Application

Here's a little something I wrote out of necessity and decided not to stop before it was completed. I'm pretty proud of it and am surprised how easy PHP was to learn. It basically helps me keep track of my gas mileage over the web so I can throw the receipt out faster, and don't have to carry a spreadsheet around. The following is from the program itself:

This program is a gas mileage database and analyzer written in PHP. It is self-contained (has a single source code file). It stores data in a simple text file in HTTP-query format. It allows users to add new records, and add new data files for different vehicles. It creates a backup before a new record is added. It also implements password protection before users can add refueling records.

Source Code:
Source Code
See it in action