title: How to convert a web form uploaded wav file to mp3 file
body: <p>I've read this question <a href="https://stackoverflow.com/questions/15099921/how-to-convert-a-web-form-uploaded-mp3-to-wav-using-php-and-ffmpeg">How to convert a web form uploaded mp3 to wav using PHP and ffmpeg?</a> that is the reverse process I need.
  I think it's necessary to use ffmpeg-php.
  How can I install it to my linux server (I think there's Debian, certainly Apache 2.2.16) and manage the ffmpeg-php extension only for one site, a virtualhost? Have I to modify php.ini or there's another way to manage the extensions?</p>