How to access variable from a function in a required file that required another file? Can I do it directly, without using $GLOBALS?

Question

So I have the following 3 files:

index.php

<?php
    require("require/functions.php");
    $g = getGroup();
    var_dump($data);
    die();
?>

functions.php

<?php
    function getGroup(){
        if(condition) $g = 1;
        else if(another condition) $g = 2;
        else if...etc
        require("data/$g.php");
        return $g;
    }
?>

An example e.g. data/1.php file:

<?php
    $data = ["Some random data"];
?>

I tried various approaches like using global $data in index.php and various other things, but didn't have any luck using this approach

I could do it by changing the getGroup() function to getGroupAndData() and returning [$g, $data], however that isn't really ideal...

Likewise I also created a global variable $temp in functions.php, used $temp = $data, then could use global $temp in the index.php file

My current preferred method is just to use $GLOBALS['data'] = $data inside the getGroup(), function, though I'm curious, is there anyway I can access this $data array from within the index.php file without having to use these workarounds?

Thanks