code: static public function examine($hash)
      {
          if (strlen($hash) == 40 && preg_match("/^[0-9]{4}/", $hash)) {
  
              $e_uid_pos = substr($hash, 0, 2);
              $e_uid_length = substr($hash, 2, 2);
              $e_uid = substr($hash, $e_uid_pos, $e_uid_length);
  
              $uid = self::decode($e_uid);
  
              preg_match('/^([0-9]{4})(.{2,' . ($e_uid_pos - 4) . '})(' . $e_uid . ')/', $hash, $excerpt);
              $partial = $excerpt[2];
  
              return array($uid, $partial);
          }
          else
          {
              /*
               * The hash is not valid
               */
              return array(false, false);
          }
      }
docs: Checks and validates a confirmation hash
  
  @param string $hash hashed string to check
  
  @return array