前端程序使用extjs写，在本地测试，发送请求到服务器时，发现存在跨域的问题，cookie也没有set成功，于是乎在这里整理一下解决过程
由于篇幅较长，不想看解决过程的可以翻到最后看总结
1.跨域允许
2.客户端无法携带跨域cookie
3.因为加了withCredentials报文头，可是客户端不知道服务器允不允许报的错
4.由于客户端不知道服务端是否允许POST请求而报的错
假设我的服务器IP是120.111.111.123
# 本地的html
# index.html
<html>
<head>
<meta charset="utf8">
</head>
<body>
<input type="button" onclick="request()" value="请求">
</body>
<script type="text/javascript" src="./ext-all.js"></script>
<script type="text/javascript">
function request(){
Ext.Ajax.request({
url: 'http://120.111.111.123/setcookie.php',
method: 'POST',
params: {
'text': 'hello world'
},
success: function(transport){
// do something
},
failure: function(transport){
alert("Error: " - transport.responseText);
}
});
}
</script>
</html>
#服务器的php文件
#path setcookie.php
<?php
session_start();
?>
点击“请求”按钮，发送请求后发现js报错
XMLHttpRequest cannot load http://120.111.111.123/setcookie.php.
Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.
Origin 'null' is therefore not allowed access.
报这个错就说明我们跨域了，不在允许的访问源，于是乎我在服务的setcookie.php加入header('Access-Control-Allow-Origin:*');允许所有源
<?php
session_start();
header('Access-Control-Allow-Origin:*');
// 功能...
// ...
然后又报错
XMLHttpRequest cannot load http://120.111.111.123/setcookie.php. Request header field X-Requested-With is not allowed by Access-Control-Allow-Headers in preflight response.
这次的报错是因为，在跨域的时候，extjs不会直接发post请求，而是先发送一个option请求，看看服务器允许什么访问头（比如是不是允许post请求），验证成功后才会发送真正的请求
#用谷歌的开发者工具抓的option报文
OPTIONS /setcookie.php HTTP/1.1
Host: 120.111.111.123
Connection: keep-alive
Pragma: no-cache
Cache-Control: no-cache
Access-Control-Request-Method: POST
Origin: null
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36
Access-Control-Request-Headers: x-requested-with
Accept: */*
Accept-Encoding: gzip, deflate, sdch
Accept-Language: zh-CN,zh;q=0.8
接下来，我们只要发送我们允许什么请求头就行了
#path /setcookie.php
session_start();
header('Access-Control-Allow-Origin:*');
header('Access-Control-Allow-Methods:OPTIONS, GET, POST'); // 允许option，get，post请求
header('Access-Control-Allow-Headers:x-requested-with'); // 允许x-requested-with请求头
header('Access-Control-Max-Age:86400'); // 允许访问的有效期
// 功能...
// ...
继续测试我们的新功能，成功的解决了跨域问题
1.png
but，cookie没有“设置成功”。而之所以没有“设置成功”，是因为cookie存在本地，但是每个cookie都有一个domain，当你本地的cookie中存在你当前访问的域时，才会被带过去，而我的index.html文件是本地访问的，即http://localhost/index.html，而cookie的域是120.111.111.123的，所以不行了。于是乎继续改
#path index.html
<html>
<head>
<meta charset="utf8">
</head>
<body>
<input type="button" onclick="request()" value="请求">
</body>
<script type="text/javascript" src="./ext-all.js"></script>
<script type="text/javascript">
function request(){
Ext.Ajax.request({
url: 'http://120.111.111.123/setcookie.php',
method: 'POST',
params: {
'text': 'hello world'
},
withCredentials: true, # 加了这个
success: function(transport){
// do something
},
failure: function(transport){
alert("Error: " - transport.responseText);
}
});
}
</script>
</html>
继续访问，报错
XMLHttpRequest cannot load http://120.111.111.123/setcookie.php.
Response to preflight request doesn't pass access control check: A wildcard '*' cannot be used in the 'Access-Control-Allow-Origin' header when the credentials flag is true.
Origin 'null' is therefore not allowed access.
The credentials mode of an XMLHttpRequest is controlled by the withCredentials attribute.
现在这个错误产生的原因就是
1.因为加入了withCredentials之后，Access-Control-Allow-Origin就不能用“*”了，既然不允许访问这个源，那我就让你发个报文头让你允许访问呗！
<?php
#path setcookie.php
session_start();
// 是否存在请求源
if(isset($_SERVER["HTTP_ORIGIN"])) {
header('Access-Control-Allow-Origin:'.$_SERVER["HTTP_ORIGIN"]);
}
header('Access-Control-Allow-Methods:OPTIONS, GET, POST');
header('Access-Control-Allow-Headers:x-requested-with');
header('Access-Control-Max-Age:86400');
// 功能...
// ...
?>
好了，上传完代码，继续测试。发送请求之后，又报错了（这错中错，一个个坑搞的大家都看得不耐烦了吧，我保证，这是最后一个报错了）
XMLHttpRequest cannot load http://120.111.111.123/setcookie.php.
Response to preflight request doesn't pass access control check: Credentials flag is 'true', but the 'Access-Control-Allow-Credentials' header is ''.
It must be 'true' to allow credentials. Origin 'null' is therefore not allowed access.
大概的意思就是说我给你发了withCredentials报文头，但是你服务器没有跟我说允许我带这个报文头，那么解决方法就是加上允许发这个报文头的报文头
# path setcookie.php
<?php
session_start();
// 是否存在请求源
if(isset($_SERVER["HTTP_ORIGIN"])) {
header('Access-Control-Allow-Origin:'.$_SERVER["HTTP_ORIGIN"]);
}
header('Access-Control-Allow-Origin:null');
header('Access-Control-Allow-Methods:OPTIONS, GET, POST');
header('Access-Control-Allow-Headers:x-requested-with');
header('Access-Control-Max-Age:86400');
header('Access-Control-Allow-Credentials:true');
// 功能...
// ...
?>
接下来进行最终的测试，biu~成功了，终于成功了！！！（0.0自己嗨起来了）
2.png
接下来总结一下，之所以跨域会引起那么多问题，都是因为耿直的客户端，发什么类型的请求都要服务器允许，而且要明文允许，允许的内容包括如下
1.跨域允许
解决方法：服务器发送允许客户端发送源的报文头
header('Access-Control-Allow-Origin:'.$_SERVER["HTTP_ORIGIN"]);
4.png
2.客户端无法携带跨域cookie
这个时候就可以在extjs中加入withCredentials
Ext.Ajax.request({
url: 'http://120.111.111.123/setcookie.php',
method: 'POST',
params: {
'text': 'hello world'
},
withCredentials: true,
success: function(transport){
// do something
},
failure: function(transport){
alert("Error: " - transport.responseText);
}
});
3.因为加了withCredentials报文头，可是客户端不知道服务器允不允许报的错（耿直的客户端）
这个时候就在服务器发送Access-Control-Allow-Credentials
header('Access-Control-Allow-Credentials:true');
4.由于客户端不知道服务端是否允许POST请求而报的错
这个时候要在服务器端加入
header('Access-Control-Allow-Methods:OPTIONS, GET, POST');
header('Access-Control-Allow-Headers:x-requested-with');
header('Access-Control-Max-Age:86400');
以上汇总起来就是
header('Access-Control-Allow-Methods:OPTIONS, GET, POST');
header('Access-Control-Allow-Headers:x-requested-with');
header('Access-Control-Max-Age:86400');
header('Access-Control-Allow-Origin:'.$_SERVER['HTTP_ORIGIN']);
header('Access-Control-Allow-Credentials:true');
header('Access-Control-Allow-Methods:GET, POST, PUT, DELETE, OPTIONS');
header('Access-Control-Allow-Headers:x-requested-with,content-type');
header('Access-Control-Allow-Headers:Origin, No-Cache, X-Requested-With, If-Modified-Since, Pragma, Last-Modified, Cache-Control, Expires, Content-Type, X-E4M-With');
代码已经放到github了，有啥问题欢迎大家指出
