Function to save the end of the trial date (on a custom meta field) when changing a subsription status to 'cancel', 'pending cancelation', 'switched' or 'expired'

save_trial_end_meta.php

<?php
/** 
 * Function to save the end of the trial date (on a custom meta field) when changing a subsription status to 'cancel', 'pending cancelation', 'switched' or 'expired'
**/

add_action('woocommerce_subscription_pre_update_status', 'save_trial_end_meta', 10, 3);
function save_trial_end_meta($old_status, $new_status, $sub){
	if(in_array($new_status, array('cancelled', 'pending-cancel', 'switched', 'expired'))){
		$sub_id = $sub->get_id();
		$trial_end_date = $sub->get_date('trial_end');
		update_post_meta($sub_id, '_trial_end_date', $trial_end_date);
	 }
}