Add Donation Receipt Opt Out Checkbox

/**

 * In this function we register a new donation field with a

 * key of `receipt_opt_out`. If the donor checks this, it means

 * they don't want to receive their donation receipt.

 */

add_action(

	'init',

	function() {

		$field = new Charitable_Donation_Field(

			'receipt_opt_out',

			array(

				'label'          => 'Donation receipt opt-out',

				'data_type'      => 'meta',

				'donation_form'  => array(

					'label'   => 'I do not need a receipt.',

					'type'    => 'checkbox',

					'default' => 0,

					'section' => 'meta',

				),

				'show_in_meta'   => true,

				'show_in_export' => true,

				'email_tag'      => false,

			)

		);

		charitable()->donation_fields()->register_field( $field );

	}

);

/**

 * This function checks whether to send the donation receipt.

 *

 * Since our checkbox was set up in such a way that people have to

 * check it to opt out of getting the receipt, we want to return true

 * if that checkbox was not checked, and false otherwise.

 *

 * @param  boolean                 $send     Whether to send the email. This defaults to true,

 *                                           so if it has been set to false already, we will

 *                                           assume we don't want to send it.

 * @param  int|Charitable_Donation $donation The donation object or ID.

 * @return boolean

 */

function ed_charitable_check_send_donation_receipt_email( $send, $donation ) {

	/* If it's already blocked, we don't need to do anything else. */

	if ( ! $send ) {

		return $send;

	}

	if ( is_int( $donation ) ) {

		$donation = charitable_get_donation( $donation );

	}

	/* We return false (i.e. we don't want to send the email) if `receipt_opt_out` is true. */

	return ! $donation->get( 'receipt_opt_out' );

}

/* Block it for normal donations. */

add_filter( 'charitable_send_donation_receipt', 'ed_charitable_check_send_donation_receipt_email', 10, 2 );

/* Block the Offline donation receipt. */

add_filter( 'charitable_send_offline_donation_receipt', 'ed_charitable_check_send_donation_receipt_email', 10, 2 );