PHP Example, 503 Header + Retry After

503.php

<?php
ob_start();

// 503 Header
header('HTTP/1.1 503 Service Temporarily Unavailable', true, 503);

// Retry-After header. Two examples of its use are:
// 1. Retry-After: 120
header('Retry-After: '.(1 * 60 * 60));
// 2. Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
header('Retry-After: '.gmdate('D, d M Y H:i:s', strtotime('+1 hour')).' GMT');