How to collect specific Youtube channel uploaded videos and use FFMPEG to convert to MP3

I am currently attempting to create a php script that can crawl a Youtube channel's uploaded videos and parse them through FFMPEG to a mp3.

.eg (http://ift.tt/1tgjds6) download each .flv then convert to mp3 using a script that can do the whole channel instead of one at a time as there are a few hundred uploads. while I have found scripts that can make FFMPEG convert to mp3 and scripts to show the uploaded videos in XML I kinda just want to figure out how to get each video automaticly, Maybe a script that can be cron'd ?