use PH7\PhpHttpResponseHeader\Header;
// Sends "200 OK" header to the browser
Http::setHeadersByCode(200);
// ...
// Send "201 Created" header
Http::setHeadersByCode(201);
// ...
// Sends "404 Not Found" to the browser
Http::setHeadersByCode(404);
// ...
// Sends "400 Bad Request" header to the browser
Http::setHeadersByCode(400);
// and so on ...

use PH7\PhpHttpResponseHeader\Header;
// Send 503, Service Temporarily Unavailable to the browser mentioning that you are doing a maintenance (good practice!)
Http::setMaintenanceCode($maintenanceTimeSeconds: 360);

use PH7\PhpHttpResponseHeader\Header;
// The HTTP server protocol
Http::getProtocol()

use PH7\PhpHttpResponseHeader\Header;
// Send "Content-Type: application/json" header to the browser
Http::setContentType("application/json");
// Send "Content-type: text/xml" to the browser
Http::setContentType("text/xml");