add-donation-amount-to-email.php

<?php
/**
 * Add donation email vairable and reset membership cost value to exclude donation.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_email_data_membership_cost_donation( $data, $email ) {
	$data['donation'] = '';

	$membership_id = $email->data['membership_id'];
	$level         = pmpro_getLevel( $membership_id );

	// Get member's order and check for donations
	$member_order = new MemberOrder();
	$member_order->getLastMemberOrder( get_current_user_id(), 'success', $membership_id );

	if ( ! empty( $member_order->id ) && function_exists( 'pmprodon_get_price_components' ) ) {
		$donation = pmprodon_get_price_components( $member_order );
		if ( ! empty( $donation['donation'] ) ) {
			$donation_amount  = pmpro_formatPrice( $donation['donation'] );
			$data['donation'] = 'Thank you for your donation of <strong>' . $donation_amount . '</strong>';

			// Set membership
			if ( ! empty( $level ) ) {
				$data['membership_cost'] = pmpro_getLevelCost( $level, true );
			}
		}
	}

	return $data;
}
add_filter( 'pmpro_email_data', 'my_pmpro_email_data_membership_cost_donation', 10, 2 );