file_exists() returns false even if file exist (remote URL)

Question

My file_exists() returns false even if provided image to check https://www.google.pl/logos/2012/haring-12-hp.png exist. Why?

Below I am pre

Answer 1

    $filename = "http://im.rediff.com/money/2011/jan/19sld3.jpg";

    $file_headers = @get_headers($filename);

    if($file_headers[0] == 'HTTP/1.1 404 Not Found') {
    //return false; 
    echo "file not found";
    }else {
    //return true;  
    echo "file found";

    }