AJAX cors跨域请求

在PHP文件上加上
header("Access-Control-Allow-Origin: *");   //全域名
header("Access-Control-Allow-Credentials: true");   //是否能够携带cookie

header("Access-Control-Allow-Methods: POST,GET,PUT,OPTIONS,DELETE");   //容许请求方式
header("Access-Control-Allow-Headers: X-Custom-Header");   //容许请求字段，由客户端决定
header("Content-Type: text/html; charset=utf-8"); //返回数据类型（ text/html; charset=utf-八、 application/json; charset=utf-8 )