// Prueba esto
$subscription_id = 5422;
$subscription = wcs_get_subscription($subscription_id);
$get_length = $subscription->get_trial_length(); //1 get_post_meta($subscription_id, '_subscription_trial_length', true);
$get_period = $subscription->get_trial_period(); // month get_post_meta($subscription_id, '_subscription_trial_period', true);
if(!empty($get_length) && !empty($get_period )){
// code here
}
//duración del retorno 1 mes, 7 días, 1 año //verificar
.