title: php check if gravatar exists header error
body: <p>I'm trying to check if a gravatar exists.  When I try the approach recommended in earlier questions, I get an error " Warning: get_headers() [function.get-headers]: This function may only be used against URLs"  Anyone seen this or see the error in my code?  PS I do not want to specify a default image for gravatar to serve as there could be more than one default possibilities if no gravatar exits.</p>
  
  <p>Also, I found a reference to error possibly being related to my ini file which I don't think my host gives me access to.  If so, is there an alternative to getheaders?  Many thanks.</p>
  
  <pre><code>$email = $_SESSION['email'];
  $email= "person@gmail.com"; //for testing
  $gravemail = md5( strtolower( trim( $email ) ) );
  $gravsrc = "http://www.gravatar.com/avatar/".$gravemail;
  $gravcheck = "http://www.gravatar.com/avatar/".$gravemail."?d=404";
  $response = get_headers('$gravcheck');
  echo $response;
  exit;
  if ($response != "404 Not Found"..or whatever based on response above){
  $img = $gravsrc;
  }
  </code></pre>