从wp帖子页面获取网址

I am trying to get a specific .m3u8 url from a JW embed post in a wordpress site.

The page contains this block of code when rendered.

....
"streamer":"",
"provider":"",
"file":"http://mysite.com:1935/live/mp4:folder/video.mp4/playlist.m3u8"}},
{"type":"download","config":{"streamer":"","provider":""}}
]});

What I am trying to do is how to take the url part

http://mysite.com:1935/live/mp4:folder/video.mp4/playlist.m3u8

and store it in a variable so that I can pass it on with my rss code.

What php function can get this URL from a block of code?

Thanks