Database-backed website configuration
I did this with a project recently, only I had even fewer settings to store. I opted for using a two column table, with each setting being it's own row.

I think there are pluses and minuses to each, but if you're dealing with such a small set of configuration options, there is not going to be a huge performance hit. To put into perspective, phpBB's config table has almost 270 rows of config options.