简要说明：新项目比较小，所以尝试了6.0版本的Laravel框架。之前的项目用的是barryvdh/laravel-cors这个包，但是目前不支持6.X系统的，所以贴出这个项目的解决方案。

自定义中间件

第一步：创建中间件

php artisan make:middleware EnableCrossRequestMiddleware

第二步：编辑中间件

<?php
namespace App\Http\Middleware;
use Closure;
class EnableCrossRequestMiddleware{
    /**
     * @param $request
     * @param Closure $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        header('Content-Type: text/html;charset=utf-8');
        header('Access-Control-Allow-Origin:*');
        header('Access-Control-Allow-Methods:POST,GET,PUT,OPTIONS,DELETE'); // 允许请求的类型
        header('Access-Control-Allow-Credentials: true'); // 设置是否允许发送 cookies
        header('Access-Control-Allow-Headers: Content-Type,Access-Control-Allow-Origin,Access-token,Content-Length,Accept-Encoding,X-Requested-with, Origin,Access-Control-Allow-Methods'); // 设置允许自定义请求头的字段

        return $next($request);

    }
}

第三步：注册中间件（全局）

<?php

namespace App\Http;

use Illuminate\Foundation\Http\Kernel as HttpKernel;

class Kernel extends HttpKernel
{
    /**
     * The application's global HTTP middleware stack.
     *
     * These middleware are run during every request to your application.
     *
     * @var array
     */
    protected $middleware = [
      //other
        \App\Http\Middleware\EnableCrossRequestMiddleware::class,
    ];