{
 "alg": "HS256",
 "typ": "JWT"
}

{
 "sub": "1234567890",
 "name": "John Doe",
 "iat": 1516239022
}

{
  "iss": "admin",     //该JWT的签发者
  "iat": 1535967430,    //签发时间
  "exp": 1535974630,    //过期时间
  "nbf": 1535967430,     //该时间之前不接收处理该Token
  "sub": "www.admin.com",  //面向的用户
  "jti": "9f10e796726e332cec401c569969e13e"  //该Token唯一标识
}

HMACSHA256(
 base64UrlEncode(header) + "." +
 base64UrlEncode(payload),
 123456
) 

<".".base64UrlEncode(payload)
   * @param string $key
   * @param string $alg  算法方式
   * @return mixed
   */
  private static function signature(string $input, string $key, string $alg = 'HS256')
  {
    $alg_config=array(
      'HS256'=>'sha256'
    );
    return self::base64UrlEncode(hash_hmac($alg_config[$alg], $input, $key,true));
  }
}

  //测试和官网是否匹配begin
  $payload=array('sub'=>'1234567890','name'=>'John Doe','iat'=>1516239022);
  $jwt=new Jwt;
  $token=$jwt->getToken($payload);
  echo "<pre>";
  echo $token;

  //对token进行验证签名
  $getPayload=$jwt->verifyToken($token);
  echo "<br><br>";
  var_dump($getPayload);
  echo "<br><br>";
  //测试和官网是否匹配end

  //自己使用测试begin
  $payload_test=array('iss'=>'admin','iat'=>time(),'exp'=>time()+7200,'nbf'=>time(),'sub'=>'www.admin.com','jti'=>md5(uniqid('JWT').time()));;
  $token_test=Jwt::getToken($payload_test);
  echo "<pre>";
  echo $token_test;

  //对token进行验证签名
  $getPayload_test=Jwt::verifyToken($token_test);
  echo "<br><br>";
  var_dump($getPayload_test);
  echo "<br><br>";
  //自己使用时候end