导致此ERROR无法打开流的因素是什么:HTTP请求失败! `?

Hi I would like to ask why i get this ERROR

I am using file_get_contents()

and I am currently receiving an ERROR

  failed to open stream: HTTP request failed! 

I would like to know how to prevent this.

I also search about curl and it is better than what I'm using right now its not matter for me if I re code or not. What i want to know is the factors why I am receiving this ERROR.

I have done searching but still i don't have clear view with this. Any comments and knowledge is well appreciated.Thanks!