Evert Pot found out an interesting thing about the basename function in PHP - it's more than just a handy shortcut for paths, it's also locale aware.

It turns out basename does a bit more than just splicing the string at the last slash, because it's locale aware. In my case I was dealing with a multi-byte UTF-8 string. It took me quite some time figuring out what was going on, because I was testing from the console which had the en_US.UTF-8 locale, and the bug was appearing on Apache, which defaults to the C locale.

He includes an example snippet of code showing how it can work with both the default (well, for Apache anyway) of the "C" locale versus the "UTF-8" locale and return different results for the same urldecoded information.