HTTP访问控制 https://developer.mozilla.org/zh-CN/docs/Web/HTTP/Access_control_CORS
解决跨域的方式有很多种，本文介绍“跨域请求附带发送cookie”
一、测试环境
前提：后台使用apache+php实现。apache设置多个虚拟主机，设置方式参考：http://www.cnblogs.com/sivkun/p/7347978.html
在http://a.sivkun.com域中/cors-cookie/目录下有文件：
1. index.php
<?php session_start(); setcookie('a.a','a.a'); setcookie('a.sivkun','a.sivkun',time()+3600*24,'/',"a.sivkun.com"); include_once 'index.html'; ?>
2. index.html
<!DOCTYPE html> <html lang="en"> <head> <title></title> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> </head> <body> <script> fetch('http://b.sivkun.com/cors-cookie/api.php', { credentials: "include" //表示发送请求附带域b.sivkun.com下cookie }).then(function (response) { console.log(response); return response.json(); }).then(function (data) { console.log('cookie',data) }) </script> </body> </html>
在http://b.sivkun.com域中/cors-cookie/目录下有文件：
1. api.php(有问题的代码)
<?php session_start();setcookie("bbbbb","bbbbb"); setcookie('b.sivkun','b.sivkun',time()+3600*24,'/',"b.sivkun.com"); echo json_encode($_COOKIE); ?>
正确的方式
1. api.php（修正后的代码）
<?php session_start(); header("Access-Control-Allow-Origin:http://a.sivkun.com"); header("Access-Control-Allow-Credentials: true"); setcookie("bbbbb","bbbbb"); setcookie('b.sivkun','b.sivkun',time()+3600*24,'/',"b.sivkun.com"); echo json_encode($_COOKIE); ?>
接下来是一步步的解决过程，不想看可以不看。
二、开启附带cookie跨域
上面的代码运行是有问题的
报错：
1.这里要求http://b.sivkun.com/cors-cookie/api.php.设置header。
index.php:1 Fetch API cannot load http://b.sivkun.com/cors-cookie/api.php.
No 'Access-Control-Allow-Origin' header is present on the requested resource.
Origin 'http://a.sivkun.com' is therefore not allowed access.
If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
修改：api.php，添加`Access-Control-Allow-Origin:*`头，允许所有跨域请求
<?php session_start(); header("Access-Control-Allow-Origin:*"); setcookie("bbbbb","bbbbb"); setcookie('b.sivkun','b.sivkun',time()+3600*24,'/',"b.sivkun.com"); echo json_encode($_COOKIE); ?>
2.这里提示如果请求使用“include”证书模式，需要把`*`改为http://a.sivkun.com。
Fetch API cannot load http://b.sivkun.com/cors-cookie/api.php.
The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'.
Origin 'http://a.sivkun.com' is therefore not allowed access.
修改：api.php
<?php session_start(); header("Access-Control-Allow-Origin:http://a.sivkun.com"); setcookie("bbbbb","bbbbb"); setcookie('b.sivkun','b.sivkun',time()+3600*24,'/',"b.sivkun.com"); echo json_encode($_COOKIE); ?>
3.接下来报错，说要添加`Access-Control-Allow-Credentials`头部，加上呗
Fetch API cannot load http://b.sivkun.com/cors-cookie/api.php.
The value of the 'Access-Control-Allow-Credentials' header in the response is '' which must be 'true' when the request's credentials mode is 'include'.
Origin 'http://a.sivkun.com' is therefore not allowed access.
api.php
<?php session_start(); header("Access-Control-Allow-Origin:http://a.sivkun.com"); header("Access-Control-Allow-Credentials: true"); setcookie("bbbbb","bbbbb"); setcookie('b.sivkun','b.sivkun',time()+3600*24,'/',"b.sivkun.com"); echo json_encode($_COOKIE); ?>
控制太输出：说明cookie是发过去了的。
最后看一下应用的cookie信息：Cookies选项中，在`a.sivkun.com`中可以看到包括`b.sivkun.com`所有的cookie信息。
接下来在控制台操作一下cookie，发现只有a.sivkun.com这个域中设置的cookie，说明浏览器限制javascript是不可以跨域操作cookie的。如下图：
