When cancelling "all levels" in PMPro, do them one at a time so CONPD works.

my_pmpro_cancel_levels_one_by_one

<?php
/**
 * This gist updates the "cancel all memberships" link on the cancel page
 * to pass the level ids into the page instead of "all".
 * This will ensure that all the levels are cancelled one by one.
 * In addition to sending a separate email for each cancellation,
 * this also ensures the $old_level parameter is sent to the
 * pmpro_cancelMembershipLevel() function so Add Ons like the
 * Cancel on Next Payment Date one continue to work.
 *
 * Add this into a custom plugin or as a code snippet:
 * https://www.paidmembershipspro.com/how-to-add-code-to-wordpress/
 */
function my_pmpro_cancel_levels_one_by_one() {
	global $current_user, $pmpro_pages, $wpdb;
	
	// Make sure PMPro is active and we're on the cancel page.
	if ( empty( $pmpro_pages ) || empty( $pmpro_pages['cancel'] ) ) {		
		return;
	}
	
	// Swap the levelstocancel REQUEST var so we cancel them all one by one
	if ( ! empty( $_REQUEST['levelstocancel'] ) && $_REQUEST['levelstocancel'] === 'all' ) {
		$old_level_ids = $wpdb->get_col("SELECT DISTINCT(membership_id) FROM $wpdb->pmpro_memberships_users WHERE user_id = '" . esc_sql( $current_user->ID ) . "' AND status = 'active'");
		$_REQUEST['levelstocancel'] = implode( ',', $old_level_ids );
		$_GET['levelstocancel'] = $_REQUEST['levelstocancel'];
		$_PUT['levelstocancel'] = $_REQUEST['levelstocancel'];		
	}
}
add_action( 'init', 'my_pmpro_cancel_levels_one_by_one', 10 );