itunes api search term file_get_contents

I have strange issue about getting info from itunes api.
So in my error log is written :
"PHP Warning: file_get_contents(https://itunes.apple.com/search?term=the-bouncing-souls&limit=1&media=music&entity=song): failed to open stream: HTTP request failed! HTTP/1.0 403 Forbidden"
But when i enter this link in adress bar its getting me content.
Also in my site when i reload page two tree times its getting me content but in first time it getting me this forbidden error.
why?

down is my code :
$response = json_decode(file_get_contents('https://itunes.apple.com/search?term='.$iartist.'&limit=1&media=music&entity=song'));