PHP function header issuing HTTP header information

// Send the 404 status code to the browser
Header ("HTTP/1.1 404 Not Found ");
Or
Header ("HTTP/1.1 404 ″);

// Permanent redirect
Header ("Location: http://weizhifeng.net/"); // The default value is 301.
// Temporary redirection
Header ("HTTP/1.1 302 Found ");
Header ("Location: http://weizhifeng.net /");

// Download an object
Header ("Content-type: text/plain '); // you can replace it with the MIME type you need.
Header ('content-Disposition: attachment; filename=%weizhifeng.txt "');
Readfile('weizhifeng.txt ');

For other header information, refer to HTTP/1.1 specification
If the output already exists before the header, use the ob_start () function.