If you really just want one file that one person will be changing, then I wouldn't go for a database, and use a file.
What kind of file? well, if you're not going to edit this manually at all, then I'd just create an array of config values in PHP, and use serialize() to convert it into one big string, and write that string to disk.
The scripts that need the config data can then open the file, unserialize the string, and boom, they have the array of config values.
BTW, that is allmost how sessions work.