摘一个微信API的签名验证函数

    /**
     * 判断验证请求的签名信息是否正确
     *
     * @param  string $token 验证信息
     * @return boolean
     */
    private function validateSignature($token) {
      $signature = $_GET['signature'];
      $timestamp = $_GET['timestamp'];
      $nonce = $_GET['nonce'];

      $signatureArray = array($token, $timestamp, $nonce);
      sort($signatureArray);

      return sha1(implode($signatureArray)) == $signature;
    }