tp5.1 前后端分离api开发时ajax跨域请求中请求头header需要注意的问题

前后端分离开发过程中，使用ajax做请求的时候需要注意几个问题

1.预请求OPTIONS问题

请求头代码改为

if($_SERVER['REQUEST_METHOD'] == 'OPTIONS'){
header('Access-Control-Allow-Origin:http://runapi.showdoc.cc');
header('Access-Control-Allow-Headers:Accept,Referer,Host,Keep-Alive,User-Agent,X-Requested-With,Cache-Control,Content-Type,Cookie,Token');
header('Access-Control-Allow-Credentials:true');
header('Access-Control-Allow-Methods:GET,POST,OPTIONS');
header('Access-Control-Max-Age:1728000');
header('Content-Type:text/plain charset=UTF-8');
header('Content-Length: 0', true);
header('status: 200');
header('HTTP/1.0 204 No Content');
exit;
}else{
header('Access-Control-Allow-Origin:http://runapi.showdoc.cc');
header('Access-Control-Allow-Credentials: true');
header("Access-Control-Allow-Methods:GET, POST, PUT,DELETE,POSTIONS");
header("Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept, Connection, User-Agent, Cookie,Token");
}