我有一个简单的PHP服务器运行在我的本地。我从前端发送请求到PHP服务器。但我得到CORS错误，即使'header（' Access-Control-Allow-Origin：* “）"出现在PHP文件中。
前端运行在8080端口，PHP服务器运行在3000端口。
下面是我得到的错误

Access to XMLHttpRequest at 'http://localhost:3000/' from origin 'http://localhost:8080' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.

这些行位于PHP文件的顶部

header('Access-Control-Allow-Origin: *'); 
header("Access-Control-Allow-Credentials: true");
header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS');
header('Access-Control-Max-Age: 1000');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token , Authorization');

知道为什么吗？