通过设置Access-Control-Allow-Origin来实现跨域访问比较简单。
例如：客户端的域名是www.client.com,而请求的域名是www.server.com
如果直接使用ajax访问，会有以下错误
XMLHttpRequest cannot load http://www.server.com/server.php. No ‘Access-Control-Allow-Origin‘ header is present on the requested resource.Origin ‘http://www.client.com‘ is therefore not allowed access.
在被请求的Response header中加入
就可以实现ajax POST跨域访问了。
代码如下：
client.html 路径：http://www.client.com/client.html
???<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> ?????<html> ??????<head> ???????<meta http-equiv="content-type" content="text/html;charset=utf-8"> ???????<title> 跨域测试 </title> ???????<script src="//code.jquery.com/jquery-1.11.3.min.js"></script> ??????</head> ????????????<body> ?????????<div id="show"></div> ?????????<script type="text/javascript"> ?????????$.post("http://www.server.com/server.php",{name:"fdipzone",gender:"male"}) ???????????.done(function(data){ ?????????????document.getElementById("show").innerHTML = data.name + ‘ ‘ + data.gender; ???????????}); ?????????</script> ??????</body> ?????</html> ?server.php 路径：http://www.server.com/server.php[php] view plain copy ???<?php ?????$ret = array( ?????????‘name‘ => isset($_POST[‘name‘])? $_POST[‘name‘] : ‘‘, ?????????‘gender‘ => isset($_POST[‘gender‘])? $_POST[‘gender‘] : ‘‘ ?????); ???????????header(‘content-type:application:json;charset=utf8‘); ?????header(‘Access-Control-Allow-Origin:*‘); ?????header(‘Access-Control-Allow-Methods:POST‘); ?????header(‘Access-Control-Allow-Headers:x-requested-with,content-type‘); ???????????echo json_encode($ret); ??????> ?
Access-Control-Allow-Origin:* 表示允许任何域名跨域访问
如果需要指定某域名才允许跨域访问，只需把Access-Control-Allow-Origin:*改为Access-Control-Allow-Origin:允许的域名
例如：
header(‘Access-Control-Allow-Origin:http://www.client.com‘);
如果需要设置多个域名允许访问，这里需要用php处理一下
例如允许 www.client.com 与 www.client2.com 可以跨域访问
server.php 修改为
1 ????????<?php ??2 ????????$ret = array( ??3 ????????????‘name‘ => isset($_POST[‘name‘])? $_POST[‘name‘] : ‘‘, ??4 ????????????‘gender‘ => isset($_POST[‘gender‘])? $_POST[‘gender‘] : ‘‘ ??5 ????????); ??6 ???????????7 ????????header(‘content-type:application:json;charset=utf8‘); ??8 ???????????9 ????????$origin = isset($_SERVER[‘HTTP_ORIGIN‘])? $_SERVER[‘HTTP_ORIGIN‘] : ‘‘; ?10 ??????????11 ????????$allow_origin = array( ?12 ????????????‘http://www.client.com‘, ?13 ????????????‘http://www.client2.com‘ ?14 ????????); ?15 ??????????16 ????????if(in_array($origin, $allow_origin)){ ?17 ????????????header(‘Access-Control-Allow-Origin:‘.$origin); ?18 ????????????header(‘Access-Control-Allow-Methods:POST‘); ?19 ????????????header(‘Access-Control-Allow-Headers:x-requested-with,content-type‘); ?20 ????????} ?21 ??????????22 ????????echo json_encode($ret); ?23 ?????????> Ajax跨域访问
原文地址：https://www.cnblogs.com/yuanwanli/p/8242304.html