get_headers() on Gravatar returning 200 instead of 404

Question

I'm passing a URL that should generate a 404 Error, using PHP's get_headers(). In fact, if I use the URL as a link, I get a 404 Error in my browser. And if I use the URL (which is to an image file) as an img src the "Network" tab of my browser shows a 404 Error status. But when I print_r the results of @get_headers( $uri ) I see that my response returns HTTP/1.0 200 OK! What's up with that?

Is this something on the web server itself? If so, what (if anything) should I communicate to the server support to get them to address the issue?

Update

The URL I am testing against is a gravatar URL: http://0.gravatar.com/avatar/4d445fd58bf07d406345bac336c3b836?s=96&d=404&r=G

Answer 1

The URL that was being sent to get_headers() had html-escaped entities, specifically & rather than an actual & ampersand token. This makes a difference to get_headers(), though its original use (<img src='{$url}'... />) didn't mind the html entities encoded version. The solution was simply to use & when building the URL.

Specific Application for Checking the Validity of a Gravatar

Since I encountered this in the context of checking the validity of a Gravatar, and the code that I was using was on some more-or-less "official" documentation, I'm posting this in case anyone else runs into the same issue and wants a cut-and-paste solution.

$url = "$host/avatar/";
$url .= $email_hash;
$url .= '?s='.$size;
$url .= '&d=404';

$gravatar_response_code = wp_cache_get( $email_hash );
if ( false === $gravatar_response_code ){
    $response = wp_remote_head ( $url );
    if ( is_wp_error( $response ) ){
        $gravatar_response_code = "error";
    } else {
        $gravatar_response_code = $response['response']['code'];
    }

    wp_cache_set( $email_hash, $gravatar_response_code, '', 300 );
}

if ( '200' == $gravatar_response_code )
    $avatar = "<img alt='{$safe_alt}' src='{$url}' class='avatar avatar-{$size} photo' height='{$size}' width='{$size}' />";

Do note that certain functions wp_cache_get(), wp_remote_head() and wp_cache_set() are WordPress-specific functions. The wp_remote_head() method of the HTTP API will call curl, get_headers() or even fopen() depending on what's available so it's 100% relevant and exhibits the same behaviours as what's documented here.

Answer 2

I did a test and I get the 404 not 200.

  $url = 'http://0.gravatar.com/avatar/4d445fd58bf07d406345bac336c3b836?s=96&d=404&r=G';
  var_dump(get_headers($url, 0));
  /* array (size=11)
  0 => string 'HTTP/1.0 404 Not Found' (length=22)
  1 => string 'Cache-Control: max-age=300' (length=26)
  2 => string 'Content-Type: text/html; charset=utf-8' (length=38)
  3 => string 'Date: Tue, 16 Apr 2013 13:46:12 GMT' (length=35)
  4 => string 'Expires: Tue, 16 Apr 2013 13:51:12 GMT' (length=38)
  5 => string 'Last-Modified: Fri, 28 Sep 2012 05:18:58 GMT' (length=44)
  6 => string 'Server: nginx' (length=13)
  7 => string 'Via: 1.1 varnish' (length=16)
  8 => string 'X-Varnish: 3241507148 3241041069' (length=32)
  9 => string 'Content-Length: 13' (length=18)
  10 => string 'Connection: close' (length=17)
  */

I did a little search and it seems that the behaviour of get_headers() depends primarily on the PHP version.

However it can be changed by changing the HTTP context options (see: HTTP context options)

Edit

Here's a very similar problem: PHP get_headers() reports different headers than CURL