Track WordPress User First Name

Hey,

Is there a way I can push user first name in the data layer?
I tried adding this in functions.php but this doesn’t work

<?php
function my_filter( array $dataLayer ): array {
global $current_user; get_currentuserinfo();
$first_name = $current_user->user_firstname;
$dataLayer[“visitorName”] = ‘$first_name’;
return $dataLayer;
}
?>