function remote_file_exists ($url)
{
   /*
   code retour erreur :
   1 : Hôte invalide
   2 : impossible de se connecter au site
   */
   
   $head = '';
   $url_p = parse_url ($url);
   
   if (isset ($url_p["host"])) {
      $host = $url_p["host"];
      
   } else {
      return 1;
      
   }
   
   if (isset ($url_p["path"])) {
      $path = $url_p["path"];
   
   } else {
      $path = '';
      
   }
   
   $fp = fsockopen ($host, 80, $errno, $errstr, 20);
   
   if (!$fp) {
      return 2;
   
   } else {
      $parse = parse_url($url);
      $host = $parse['host'];
   
      fputs($fp, "HEAD ".$url." HTTP/1.1\r\n" );
      fputs($fp, "HOST: ".$host."\r\n" );
      fputs($fp, "Connection: close\r\n\r\n" );
      
      $headers = '';
      
      while (!feof ($fp))
      {
         $headers .= fgets ($fp, 128);
         
      }
   }
   
   fclose ($fp);
   $arr_headers = explode("\n", $headers);
   $return = false;
   
   if (isset ($arr_headers[0])) {
      $return = strpos ($arr_headers[0], "404" ) === false;
      
   }
   
   return $return;
}



/* utilisation */
$url = "http://www.google.it/intl/it_it/images/logo.gif";
if (remote_file_exists ($url)) {
   print ($url . " file exists!" );

} else {
   print ($url . " file doesn't exist!" );
   
}