Add the enddate to Mailchimp Merge fields if it exists otherwise return "N/A"

pmpro-mc-merge-enddate.php

<?php

add_action( 'pmpro_mailchimp_listsubscribe_fields', 'my_pmpro_mailchimp_listsubscribe_fields', 10, 2 );
function my_pmpro_mailchimp_listsubscribe_fields( $fields, $user ) {
	// Get user level
	$level = pmpro_getMembershipLevelForUser( $user->ID );
	// Declare variable and set default
	$expiration_date = 'N/A';
	// Update variable value if level has an expiration date
	if ( ! empty( $level->enddate ) ) {
		$expiration_date = date( 'd/m/Y', $level->enddate );
	}
	// Create new ENDDATE field
	$new_fields = array(
		'ENDDATE' => $expiration_date,
	);
	// join existing fields with new fields
	$fields = array_merge( $fields, $new_fields );

	return $fields;
}


/*
	(Optional) Tell PMPro MailChimp to always synchronize user profile updates. By default it only synchronizes if the user's email has changed.

	Requires PMPro Mailchimp v2.0.3 or higher.
*/
add_filter( 'pmpromc_profile_update', '__return_true' );