How can server administration settings affect the ability to access certain environment variables in PHP scripts?

Server administration settings can affect the ability to access certain environment variables in PHP scripts by restricting access to them or by not passing them to the PHP environment. To solve this issue, you can use the PHP $_SERVER superglobal array to directly access the environment variables you need, regardless of the server settings.

$custom_variable = $_SERVER['CUSTOM_VARIABLE'];
echo $custom_variable;