How to determine if gravatar.com request returns 404

Question

I'm stuck on this. This code pulls a gravatar image for the $source argument. I'm trying to determine how to pass the url to gravatar and determine if the result is an image or a 404.

If its a 404, I don't want to copy default.png into a new image, I just want to use the default.png

    function cb_gravatar($source) {

    $time = 1209600; //The time of cache(seconds)
    preg_match('/avatar\/([a-z0-9]+)\?s=(\d+)/', $source, $tmp);
    $abs = TEMPLATEPATH.
    '/gravatar-cache/'.$tmp[1].
    '.jpg';
    $url = get_bloginfo('template_directory').
    '/gravatar-cache/'.$tmp[1].
    '.jpg';
    $default = get_bloginfo('template_directory').
    '/gravatar-cache/'.
    'default.png';

    if (!is_file($abs) || (time() - filemtime($abs)) > $time) {
        //copy('http://www.gravatar.com/avatar/'.$tmp[1].'?s=64&d='.$default.'&r=G',$abs);
        //IF REQUEST RETURNS A 404 USE THE LOCAL DEFAULT.PNG
        copy('http://www.gravatar.com/avatar/'.$tmp[1].
        '?s=32&d=404&r=G', $abs);

    }

    if (filesize($abs) < 500) {
        copy($default, $abs);
    }

    return '<img alt="" src="'.$url.
    '" class="avatar avatar-'.$tmp[2].
    '" width="'.$tmp[2].
    '" height="'.$tmp[2].
    '" />';

}

Answer 1

Gravatar have added an option to the 'd' parameter, meaning that if you pass in d=404, you get a 404 page (instead of some 302 redirect to a default picture) if there's no picture, rather than having to use heuristics.

Though you said you know about the d parameter, do you know it actually returns a redirect header when applicable? So, the following yields 302 Found because the avatar does not exist:

http://www.gravatar.com/avatar/3b3be63a4c2a439b013787725dfce802?d=http%3A%2F%2Fwww.google.com%2Fimages%2Flogo.gif

    HTTP/1.1 302 Found  
...  
Last-Modified: Wed, 11 Jan 1984 08:00:00 GMT  
Location: http://www.google.com/images/logo.gif  
Content-Length: 0  
...  
Expires: Sun, 26 Jul 2009 23:18:33 GMT  
Cache-Control: max-age=300

Seems to me that all you need to do is add that d parameter and check the HTTP result code then.