Using FFMpeg av_read_frame in PHP?

I'm hoping to incorporate FFMpeg in a PHP script. My understanding is that the two best solutions are to use the command line via exec() and extract results or use PHP-FFMpeg (http://ift.tt/1cuzO85).

What I want to do is walk through a video frame-by-frame, and I think I need to use av_read_frame(). What's the best way to use that from PHP? I don't think it's available from the command line or PHP-FFMpeg. Should I write a C program (using XCode) to do what I want and call it from my PHP script?

Thanks!