Hello,
If:
function custom($var) {
echo $errors[$var];
}
And:
$errors = array();
$errors['fn'] = 'You forgot to enter your name.';
Then:
custom('fn');
Why doesn’t it work? Am I needing to address scope? If so, how would I do this?
Thanks in advance for any help you can provide 
Yep, it’s a scope problem.
Two possible solutions:
function custom($var) {
$errors = array();
$errors['fn'] = 'You forgot to enter your name.';
echo $errors[$var];
}
custom('fn');
function custom($var, $errors) {
echo $errors[$var];
}
$errors = array();
$errors['fn'] = 'You forgot to enter your name.';
custom('fn', $errors);
Beauty! Used your second example and fixed everything!
Cheers 