How can constants be defined once and reused through all files?

Question

I\'m trying to set up a site that has many reusable headers/footers, style information, etc. Is there anyway to define a global constant/function that can be reused from any

Answer 1

what's the problem?

define('ROOT_DIR', '/var/www/my_page/');
function includeAll() {
    include_once(ROOT_DIR . 'file1.php');
    include_once(ROOT_DIR . 'file2.php');
    include_once(ROOT_DIR . 'file3.php');
    include_once(ROOT_DIR . 'file4.php');
}