zencoder notifications json
===

I'm working with some videos on PHP, using zencoder to encode the videos, save them on s3 and then notify my site back when it's all done.
Everything is working until I have to process the notifications returned as json and pull out the new url to the saved video.

this:

    $notification = $zencoder->notifications->parseIncoming();

    if($notification->job->state == "finished")
    {
    	$encode_id=$notification->job->id;
    }
works fine. I just need some pointers on accessing the url.

The notification is sent as:
    {"output":     {"frame_rate":30.0,"label":"video_id_","total_bitrate_in_kbps":3115,"md5_checksum":null,"channels":"2","audio_codec":"aac","duration_in_ms":4225,"video_codec":"h264","url":"http://my_url/597bd3592bf4a9d70f04dc676c44de6d.mp4","thumbnails":[{"label":null,"images":[{"url":"http://my_url/_key__0000.png","format":"PNG","dimensions":"640x360","file_size_bytes":482422}]}],"video_bitrate_in_kbps":3052,"width":640,"format":"mpeg4","height":360,"audio_sample_rate":44100,"state":"finished","audio_bitrate_in_kbps":63,"id":41424918,"file_size_in_bytes":1625847},"input":{"frame_rate":30.0,"total_bitrate_in_kbps":3867,"md5_checksum":null,"channels":"2","audio_codec":"aac","duration_in_ms":4167,"video_codec":"h264","video_bitrate_in_kbps":3764,"width":640,"format":"mpeg4","height":360,"audio_sample_rate":44100,"state":"finished","audio_bitrate_in_kbps":103,"id":22371764,"file_size_in_bytes":2028809},"job":{"created_at":"2012-07-14T22:25:08Z","test":true,"updated_at":"2012-07-14T22:25:47Z","submitted_at":"2012-07-14T22:25:08Z","pass_through":null,"state":"finished","id":22377083}}

but something like: 	$video_file=$notification->output->url; doesn't. 
What am I missing?
