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);
?>