title: Convert .mp4 to .mp3 using pure PHP
body: <p>How do I convert a video (.mp4) from an external site (ex: youtube.com) to an .mp3 using PHP without wasting a lot of resources? So similar to <a href="http://youtube-mp3.org/" rel="nofollow">http://youtube-mp3.org/</a>, they are able to convert it very easily. </p>
  
  <p>Thanks.</p>