1. 什么是 CORS

CORS（Cross-Origin Resource Sharing 跨源资源共享），当一个请求 url 的协议、域名、端口三者之间任意一与当前页面地址不同即为跨域。

2. 解决方法

一般而言，只需要加入以下三行代码即可解决

//指定允许其他域名访问
header(‘Access-Control-Allow-Origin:’);
//响应类型
header('Access-Control-Allow-Methods:’);
//响应头设置
header(‘Access-Control-Allow-Headers:x-requested-with,content-type’);

3.具体操作

在对应目录下创建此类= application\api\behavior\CORS.php

<?php


namespace app\api\behavior;


use think\Response;

class CORS
{
    public function appInit(){
        header('Access-Control-Allow-Origin:*');
        header('Access-Control-Allow-Methods:*');
        header('Access-Control-Allow-Headers:x-requested-with,content-type');
    }
}

来到tags.php

    // 应用初始化
    'app_init'     => [
        'app\\api\\behavior\\CORS'
    ],

由于我后期还遇到了另一个跨域警告，又对此有所修改

 public function appInit(){

        // Allow from any origin
        if (isset($_SERVER['HTTP_ORIGIN'])) {
            // Decide if the origin in $_SERVER['HTTP_ORIGIN'] is one
            // you want to allow, and if so:
            header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
            header('Access-Control-Allow-Credentials: true');
            header('Access-Control-Max-Age: 86400');    // cache for 1 day
        }

        // Access-Control headers are received during OPTIONS requests
        if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {

            if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
                // may also be using PUT, PATCH, HEAD etc
                header("Access-Control-Allow-Methods: GET, POST, OPTIONS");

            if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
                header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");

            exit(0);
        }

        /*header('Access-Control-Allow-Origin:*');
        header('Access-Control-Allow-Methods:*');
        header('Access-Control-Allow-Headers:*');//x-requested-with,content-type
        header('Access-Control-Allow-Credentials:true');*/
    }