Fetch user PM settings.
user_pm_settings( int $user_id [, string $key ] ) : mixed
$user_id (int) (Required) User ID.
$key (string) (Optional) The key of one column. Default value: null
(array|string) Associative array of all data or one column by key.
$pm_settings = user_pm_settings(1);
echo $pm_settings['user_pm_email_notify'];
// 1