Set Default Donation Amount Per Campaign

/**

 * Customize the default donation amount on a per campaign basis.

 *

 * @see https://github.com/Charitable/library/blob/master/donation-form/set-default-donation-amount.php

 *

 * @param  float|int           $amount   The amount to be filtered. $0 by default.

 * @param  Charitable_Campaign $campaign The instance of `Charitable_Campaign`.

 * @return float|int

 */

function ed_charitable_set_default_donation_amount_per_campaign( $amount, Charitable_Campaign $campaign ) {

	switch ( $campaign->ID ) {

		// Default amount for campaign with ID #111

		case 111:

			$amount = 25;

			break;

		// Default amount for campaign with ID #222

		case 222:

			$amount = 50;

			break;

		// Default amount for campaign with ID #333

		case 333:

			$amount = 75;

			break;

		// The default amount for all other campaigns.

		default:

			$amount = 15;

	}

	return $amount;

}

add_filter( 'charitable_default_donation_amount', 'ed_charitable_set_default_donation_amount_per_campaign', 10, 2 );