Pass global variable into function not working - php

Question

I am trying to use allow my custom API endpoint to upload files to a custom directory based on information sent in the request body. It is coming through fine but I am not getting it to pass into the directory properly. I have tried getting the studentid from the request body and then calling that as a global in my function but it is not working.
add_filter("wcra_upload_callback", "wcra_upload_callback_handler");
function wcra_upload_callback_handler($request) {
if (!function_exists('wp_handle_upload')) {
require_once(ABSPATH.'wp-admin/includes/file.php');
}
$studentid = $request['studentid'];
function studentresultsdir($dir) {
global $studentid;
$mydir = 'https://example.com/wp-content/uploads/studentresults/';
$dir['path'] = $mydir;
$dir['url'] = $mydir;
$dir['subdir'] = $studentid;
var_dump($dir);
return $dir;
}
add_filter("upload_dir", "studentresultsdir");
$uploadedfile = $_FILES['file'];
$upload_overrides = array('test_form' => false);
$movefile = wp_handle_upload($uploadedfile, $upload_overrides);
if ($movefile && !isset($movefile['error'])) {
echo __('File is valid, and was successfully uploaded.', 'textdomain')."\n";
var_dump($movefile);
} else {
echo $movefile['error'];
}
remove_filter("upload_dir", "studentresultsdir");
}
My var_dump of $dir is giving me an empty subdirectory. I think this is the cause of my "unable to create directory" error too but need to work this step out first.
Just wanted to add that I will be adding authentication checks once I get this working.

Answer 1

I managed to solve this particular error by moving the global variable outside of all functions.
add_filter("wcra_upload_callback", "wcra_upload_callback_handler");
$studentid = '';
function wcra_upload_callback_handler($request) {
if (!function_exists('wp_handle_upload')) {
require_once(ABSPATH.'wp-admin/includes/file.php');
}
global $studentid;
$studentid = $request['studentid'];
function studentresultsdir($dir) {
global $studentid;
$mydir = 'https://example.com/wp-content/uploads/studentresults/';
$dir['path'] = $mydir;
$dir['url'] = $mydir;
$dir['subdir'] = '/'.$studentid;
var_dump($dir);
return $dir;
}
add_filter("upload_dir", "studentresultsdir");
$uploadedfile = $_FILES['file'];
$upload_overrides = array('test_form' => false);
$movefile = wp_handle_upload($uploadedfile, $upload_overrides);
if ($movefile && !isset($movefile['error'])) {
echo __('File is valid, and was successfully uploaded.', 'textdomain')."\n";
var_dump($movefile);
} else {
echo $movefile['error'];
}
remove_filter("upload_dir", "studentresultsdir");
}