Determining the length (in an audio sense) of an MP3

Hi, I am trying to determine the length (in terms of seconds) of an MP3 file. I have seen the ID3 pear project, but I didn't see anything there to tell me how long the song was. There is a fileinfo pecl project, but it doesn't mention MP3s and I couldn't find any good documentation for it (looking at the pecl site). Does anyone know of an decent way to determine the length of a song? What about other formats (oog, wav, etc?). thanks paul