ajax 设置Access-Control-Allow-Origin实现跨域访问

通过设置Access-Control-Allow-Origin来实现跨域访问

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.

header('Content-Type: text/html;charset=utf-8');
header('Access-Control-Allow-Origin:*'); // *代表允许任何网址请求
header('Access-Control-Allow-Methods:POST,GET,OPTIONS,DELETE'); // 允许请求的类型
header('Access-Control-Allow-Credentials: true'); // 设置是否允许发送 cookies
header('Access-Control-Allow-Headers: Content-Type,Content-Length,Accept-Encoding,X-Requested-');