For a 302 Found, i.e. a temporary redirect do:
header('Location: http://www.example.com/home-page.html');
// OR: header('Location: http://www.example.com/home-page.html', true, 302);
exit;
If you need a permanent redirect, aka: 301 Moved Permanently, do:
header('Location: http://www.example.com/home-page.html', true, 301);
exit;
For more info check the PHP manual for the header function Doc. Also, don’t forget to call exit; when using header('Location: ');
But, considering you are doing a temporary maintenance (you don’t want that search engines index your page) it’s advised to return a 503 Service Unavailable with a custom message (i.e. you don’t need any redirect):
<?php
header("HTTP/1.1 503 Service Unavailable");
header("Status: 503 Service Unavailable");
header("Retry-After: 3600");
?><!DOCTYPE html>
<html>
<head>
<title>Temporarily Unavailable</title>
<meta name="robots" content="none" />
</head>
<body>
Your message here.
</body>
</html>