What specific error are you getting with TCPMP? Some encodings within TCPMP are supported with plugins that you have to download separately. AAC encodings are not officially supported yet, but are available from unofficial places. Some encodings (such as QDesign/Sorensen) are not supported at all. M4V generally use XviD or H.264 video encoding and AAC audio encoding. TCPMP is the only program that I am aware of that comes close to playing H.264 encoded video, but TCPMP uses an ffmpeg library that has not yet been optimized.
A "php" file is not a media file, it is a server-side script that apparently is serving the media file that you want. This is one of the difficulties for playing a podcast outside of a Pocket PC-based aggregator like FeederReader.
When played within FeederReader, the "php" file is played based on the MIME type given by the podcast feed.
I think it would be very difficult to play a PHP file outside of FeederReader because the MIME type is not available.
Greg Smith
Author, FeederReader - Pocket PC *direct* RSS text, audio, video, podcasts
www.FeederReader.com - Download on the Road