Maintenance mode with PHP

maintanance_mode.php

<?php
function maintenance($mode = FALSE){
    if($mode){
        if(basename($_SERVER['SCRIPT_FILENAME']) != 'maintenance.php'){
            header("Location: http://example.com/maintenance.php");
            exit;
        }
    }else{
        if(basename($_SERVER['SCRIPT_FILENAME']) == 'maintenance.php'){
            header("Location: http://example.com/");
            exit;
        }
    }
}
?>

Maintenance mode with PHP

When updating your site, it is generally a good thing to temporarily redirect your users to a “Maintenance” page so they will not see any critical info such as error messages.
This is generally done using an .htaccess file, but it can be done easily with PHP: