PHP: @get_headers response

How much can I rely that the following code will work every time I get a 200 request response? In order words, will the response string have always the same structure when 200? Such as HTTP/1.0 200 OK for the first index.

$response = @get_headers('www.domain.com');

function is200(){
 return (substr($response[0], -6, 3) === '200' ? true : false);
}