把项目里的 laravel 5.5.39 升级到 5.5.45 后，出现如下报错：
ErrorException
openssl_encrypt() expects parameter 1 to be string, array given
vendor/laravel/framework/src/Illuminate/Encryption/Encrypter.php in handleError at line 91
vendor/sentry/sentry/lib/Raven/Breadcrumbs/ErrorHandler.php in handleError at line 34
vendor/sentry/sentry/lib/Raven/Breadcrumbs/ErrorHandler.php in openssl_encrypt
vendor/laravel/framework/src/Illuminate/Encryption/Encrypter.php in encrypt at line 91
vendor/laravel/framework/src/Illuminate/Cookie/Middleware/EncryptCookies.php in encrypt at line 139
vendor/laravel/framework/src/Illuminate/Cookie/Middleware/EncryptCookies.php in handle at line 66
vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php in IlluminatePipeline{closure} at line 149
vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php in IlluminateRouting{closure} at line 53
vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php in then at line 102
vendor/laravel/framework/src/Illuminate/Routing/Router.php in runRouteWithinStack at line 660
vendor/laravel/framework/src/Illuminate/Routing/Router.php in runRoute at line 635
vendor/laravel/framework/src/Illuminate/Routing/Router.php in dispatchToRoute at line 601
vendor/laravel/framework/src/Illuminate/Routing/Router.php in dispatch at line 590
vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php in IlluminateFoundationHttp{closure} at line 176
vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php in IlluminateRouting{closure} at line 30
vendor/barryvdh/laravel-debugbar/src/Middleware/InjectDebugbar.php in handle at line 58
vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php in IlluminatePipeline{closure} at line 149
vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php in IlluminateRouting{closure} at line 53
vendor/fideloper/proxy/src/TrustProxies.php in handle at line 56
vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php in IlluminatePipeline{closure} at line 149
vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php in IlluminateRouting{closure} at line 53
vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php in handle at line 30
vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php in IlluminatePipeline{closure} at line 149
vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php in IlluminateRouting{closure} at line 53
vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php in handle at line 30
vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php in IlluminatePipeline{closure} at line 149
vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php in IlluminateRouting{closure} at line 53
vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ValidatePostSize.php in handle at line 27
vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php in IlluminatePipeline{closure} at line 149
vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php in IlluminateRouting{closure} at line 53
vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/CheckForMaintenanceMode.php in handle at line 46
vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php in IlluminatePipeline{closure} at line 149
vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php in IlluminateRouting{closure} at line 53
vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php in then at line 102
vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php in sendRequestThroughRouter at line 151
vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php in handle at line 116
public/index.php at line 55
观察上面的堆栈记录，并且打断点排查，终于确定是由于 Cookie 序列化加密导致的问题。
查阅 laravel 5.5 upgrade 官方文档，laravel 5.5.42 版开始为了防止 PHP 对象的序列化/反序列化漏洞被利用，不再对 Cookie 值进行自动的序列化和反序列化处理。
举个栗子：
Cookie::queue('user', ['id' => 1, 'name' => 'admin'], 720, '/')
Laravel 更新到 v5.5.42 后，因为 Laravel 不再自动对 Cookie 值 ['id' => 1, 'name' => 'admin'] 进行序列化处理，而 openssl_encrypt ( string $data ... ) 只能加密字符串数据，这个时候程序就会抛出错误：openssl_encrypt() expects parameter 1 to be string, array given。
解决方法：
- 新版里面在中间件 AppHttpMiddlewareEncryptCookies 新增静态属性 $serialize，当设置为 true 时可开启 Cookie 值的自动序列化和反序列化处理。
/** * Indicates if cookies should be serialized. * * @var bool */ protected static $serialize = true;
- 【推荐】将 Cookie 值使用 JSON 函数编码成字符串后再进行存储（获取 Cookie 值后需调用 json_decode 函数进行解码）。
Cookie::queue('user', json_encode(['id' => 1, 'name' => 'admin']), 720, '/');
首发于知乎专栏《PHP和Laravel学习》：https://zhuanlan.zhihu.com/p/60861964