Get full Site URL including "HTTP" or "HTTPS".

config.php

function siteURL()
{
    $protocol = (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off' || $_SERVER['SERVER_PORT'] == 443) ? "https://" : "http://";
    $domainName = $_SERVER['HTTP_HOST'].'/';
    return $protocol.$domainName;
}