youtube api is no longer available

I built recently a php app that takes the url of a youtube video and gets his duration using the youtube api. The Url I call is :

http://gdata.youtube.com/feeds/api/videos/zK0C1yxGDsw

it has always worked , until couple of days ago , where I get this error :

DOMDocument::load(http://gdata.youtube.com/feeds/api/videos/zK0C1yxGDsw): failed to open stream: HTTP request failed! HTTP/1.0 410 Gone

when I try to access the url :

http://gdata.youtube.com/feeds/api/videos/zK0C1yxGDsw

I get : no longer available.