Custom variable which can be used on each page like super globals?

Question

I want a variable to be superglobal, but as am using procedural style I don't think I can make one of my own, so basically the question is that am using a query to retrieve all security control of my website from security table, am checking whether maintenance mode is on/off, if it's on am redirecting it to website under maintenance page, so on each page I need to check the status of variable $maintenance_status, for doing this, i need to call that query on each page, or else am getting an error that undefined variable, moreover if am making a function and including that function file in other pages, it is showing me that $db_connect(which is my db connection variable) is undefined, am including my pages in this sequence

include_once('connection.php');
include_once('functions.php');
 /*other scripts goes here*/

Any idea how to pull this status on each page? I thought to make a new file for common queries but is ait a clean solution? moreover I guess am not understanding includes, if I included connection.php before functions.php than why my functions.php is showing undefined variable $db_connect?

Answer 1

Without more code context on where within your files you are getting the errors, it will be hard to provide any advice. For example, is your reference to $db_connect done from inside a function? If it is, than it will not work unless you have a global $db_connect declaration within that function (to use the $db_connect in the global scope rather than the undefined $db_connect in the function's scope).

While I don't prefer using such global declarations within functions for a number of reasons (I would rather use dependency injection, or get the DB connection via a static singleton function call), that is probably a lesson for another time.

You might be best served anyway to make your query in some sort of init script (like after your connection.php inlcude) and define a constant regarding whether maintenance mode if on or off. Something like this

// assuming you have already made DB query and have a value of true/false on a variable called $is_maint_mode
define('MAINT_MODE', $is_maint_mode);

This would give you a constant MAINT_MODE that is globally available to your code.

Answer 2

You can use a constant for that by using define(). Defines can be set once per script execution and can not be changed during one script execution. They are superglobal - also across files which are being included.

See http://php.net/define or just

define('MY_CONSTANT', 'whatever');
define('MY_OTHER_CONSTANT', false);

function foo() {
    if (MY_OTHER_CONSTANT !== true) {
        echo MY_CONSTANT;
    }
}

foo();