二：代码实现

class JWT {
          private static $header=array(
            ‘alg‘=>‘SHA256‘, //生成signature的算法
            ‘typ‘=>‘JWT‘  //类型
          );
          private static $payload= array(
          );
        //使用HMAC生成信息摘要时所使用的密钥
          private static $key=‘123456‘;
          public function getToken(){
              //这是第一部分
              $base64 = json_encode(self::$header);
              $baseencode = base64_encode($base64);

              self::$payload[‘time‘]=time()+3600;//过期时间
              self::$payload[‘uid‘]=110;
              $basepayLoad64=json_encode(self::$payload);
              $base64payload = base64_encode($basepayLoad64);
              //生成签名
              $input = $baseencode.".".$base64payload;
              $token = $this->signature($input,self::$key,self::$header[‘alg‘]);
              $token = base64_encode($token);
              $token = $input.".".$token;
              return $token;
          }

          public function signature($input,$key,$alg){
              $base64 = hash_hmac($alg,$input,$key,true);
              
              return $base64;
          }
          //如何做校验
          public function check($token){
              list($base64,$payload,$signature)=explode(".",$token);

              $input = $base64.".".$payload;
              $newSignature = $this->signature($input,self::$key,self::$header[‘alg‘]);
              $newSignature = base64_encode($newSignature);

              if($newSignature == $signature){
                  $str = base64_decode($payload);
                  $arr = json_decode($str,true);
                  print_r($arr);
              }

          }
    }
    $objjwt = new JWT();
    $accessToken = $objjwt->getToken();

    $objjwt->check($accessToken);
?>