Add Campaign Link

/**

 * Add a link back to the campaign from the donation receipt.

 */

function ed_add_campaign_link_to_receipt( $donation ) {

    $campaigns = $donation->get_campaign_donations();

    // We're just linking to the first campaign.

    $campaign_donation = current( $campaigns );

    ob_start();

?>    

<p><a href="<?php echo get_permalink( $campaign_donation->campaign_id ) ?>"><?php printf( __( 'Back to %s', 'your-namespace' ), $campaign_donation->campaign_name ) ?></a></p>

<?php

    echo ob_get_clean();

}

add_action( 'charitable_donation_receipt_before', 'ed_add_campaign_link_to_receipt' );