从https://jwt.io/中找到目前github上目前star最多的jwt包：

https://github.com/firebase/php-jwt其文档：

PHP-JWT

A simple library to encode and decode JSON Web Tokens (JWT) in PHP, conforming to RFC 7519.

Installation

Use composer to manage your dependencies and download PHP-JWT:

composer require firebase/php-jwt

Example

<?php
use \Firebase\JWT\JWT;

$key = "example_key";
$payload = array(
    "iss" => "http://example.org",
    "aud" => "http://example.com",
    "iat" => 1356999524,
    "nbf" => 1357000000
);

/**
 * IMPORTANT:
 * You must specify supported algorithms for your application. See
 * https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-40
 * for a list of spec-compliant algorithms.
 */
$jwt = JWT::encode($payload, $key);
$decoded = JWT::decode($jwt, $key, array('HS256'));

print_r($decoded);

/*
 NOTE: This will now be an object instead of an associative array. To get
 an associative array, you will need to cast it as such:
*/

$decoded_array = (array) $decoded;

/**
 * You can add a leeway to account for when there is a clock skew times between
 * the signing and verifying servers. It is recommended that this leeway should
 * not be bigger than a few minutes.
 *
 * Source: http://self-issued.info/docs/draft-ietf-oauth-json-web-token.html#nbfDef
 */
JWT::$leeway = 60; // $leeway in seconds
$decoded = JWT::decode($jwt, $key, array('HS256'));

?>

Example with RS256 (openssl)

<?php
use \Firebase\JWT\JWT;

$privateKey = <<<EOD
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----
EOD;

$publicKey = <<<EOD
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC8kGa1pSjbSYZVebtTRBLxBz5H
4i2p/llLCrEeQhta5kaQu/RnvuER4W8oDH3+3iuIYW4VQAzyqFpwuzjkDI+17t5t
0tyazyZ8JXw+KgXTxldMPEL95+qVhgXvwtihXC1c5oGbRlEDvDF6Sa53rcFVsYJ4
ehde/zUxo6UvS7UrBQIDAQAB
-----END PUBLIC KEY-----
EOD;

$payload = array(
    "iss" => "example.org",
    "aud" => "example.com",
    "iat" => 1356999524,
    "nbf" => 1357000000
);

$jwt = JWT::encode($payload, $privateKey, 'RS256');
echo "Encode:\n" . print_r($jwt, true) . "\n";

$decoded = JWT::decode($jwt, $publicKey, array('RS256'));

/*
 NOTE: This will now be an object instead of an associative array. To get
 an associative array, you will need to cast it as such:
*/

$decoded_array = (array) $decoded;
echo "Decode:\n" . print_r($decoded_array, true) . "\n";
?>

构建自定义类

<?php
namespace app\lib\tools;

use \Firebase\JWT\JWT;

/**
 * 单例 一次请求中所有使用jwt的地方都是一个用户
 *
 */
class JwtAuth
{
    private $token;
    private static $instance;

    private $iss = 'api.tets.com'; //签发人
    private $aud = 'api.tets.com'; //受众
    private $key = '#dsafasieg92fsdyhb3290&$#%#@342';

    private $uid;
    /**
     * 单例模式 JwtAuth句柄
     */
    public static function getInstance()
    {
        if (is_null(self::$instance)) {
            self::$instance = new self();
        }

        return self::$instance;
    }

    private function __construct()
    {
    }

    private function __clone(){
    }

    public function encode()
    {
        $time = time();
        $payload = array(
            "iss" => $this->iss,
            "aud" => $this->aud,
            "iat" => $time,
            "nbf" => $time,
            "uid" => $this->uid
        );
        $this->token = $jwt = JWT::encode($payload, $this->key);

        return $this;
    }

    public function getToken()
    {
        return (string)$this->token;
    }

    public function setToken($token)
    {
        $this->token = $token;
        return $this;
    }

    public function setUid($uid)
    {
        $this->uid = $uid;
        return $this;
    }

}

    public function decode()
    {
        $token = Request::instance()->param('token');
        $key = '#dsafasieg92fsdyhb3290&$#%#@342';
//        JWT::$leeway = 60; // $leeway in seconds
        $decoded = JWT::decode($token, $key, array('HS256'));
        dd ($decoded);
    }

    public function login()
    {
        //通过认证后获取uid为304
        $uid = 304;
        $jwtAuth = JwtAuth::getInstance();
        $token = $jwtAuth->setUid($uid)->encode()->getToken();

        return [
            'status' => 100,
            'message' => '成功',
            'token' => $token
        ];

    }

文档中的案例写的很明白，该如何去使用，重点是理解JWT这种模式的优缺点和观看其源码自己实现JWT的构建与封装
https://www.cnblogs.com/yuanrw/p/10089796.html
https://www.jianshu.com/p/792f71bb52dd