Set up an Custom AffiliateWP Integration

custom-integration.php

<?php

/**
* Registers a custom integration in AffiliateWP
**/
add_filter( 'affwp_extended_integrations', function( $integrations ) {

	// Register the custom integration
	$integrations['custom_integration'] = array(
		'name'     => 'Custom Integration',
		'class'    => 'Custom_Integration',
		'file'     => 'path/to/integration/Custom_Integration.php',
		'enabled'  => true,
		'supports' => array( 'sales_reporting' ), // Only enable sales reporting if your plugin will actually support sales data methods in the base class!
	);

	return $integrations;
} );

Custom_Integration.php

<?php
/**
 * Custom Integration Class
 *
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Class Custom_Integration
 * Use this class to ext
 */
class Custom_Integration extends \Affiliate_WP_Base {


	/**
	 * The context for referrals. This refers to the integration that is being used.
	 *
	 * @access  public
	 * @since   1.2
	 */
	public $context = 'custom_integration';

	/**
	 * Gets the total order count for this integration.
	 *
	 * @since 2.5
	 *
	 * @param string|array $date {
	 *     Optional. Date string or start/end range to retrieve orders for. Default empty.
	 *
	 *     @type string $start Start date to retrieve orders for.
	 *     @type string $end   End date to retrieve orders for.
	 * }
	 * @return int The total order count.
	 */
	// public function get_total_order_count( $date = '' ) {}

	/**
	 * Gets the total sales for this integration.
	 *
	 * @since 2.5
	 *
	 * @param string|array $date {
	 *     Optional. Date string or start/end range to retrieve orders for. Default empty.
	 *
	 *     @type string $start Start date to retrieve orders for.
	 *     @type string $end   End date to retrieve orders for.
	 * }
	 * @return int|float The total sales.
	 */
	// public function get_total_sales( $date = '' ) {}

	/**
	 * Retrieves a list of orders based on the provided dates.
	 *
	 * @since 2.5
	 *
	 * @param string|array $date {
	 *     Optional. Date string or start/end range to retrieve orders for. Default empty.
	 *
	 *     @type string $start Start date to retrieve orders for.
	 *     @type string $end   End date to retrieve orders for.
	 * }
	 * @return array
	 */
	// public function get_orders( $date = '' ) {}

	/**
	 * Retrieves the order total for the specified order ID
	 *
	 * @since 2.5
	 *
	 * @param int $order_id The order ID
	 * @return float|int The order total
	 */
	// public function get_order_total( $order_id = 0 ) {}
}

new Custom_Integration;

You can also extend an existing integration, and override its functionality by extending any integration class directly.

EDD Example:

/**
 * Class Custom_Integration
 * Use this class to ext
 */
class Custom_Integration extends \Affiliate_WP_EDD {


	/**
	 * The context for referrals. This refers to the integration that is being used.
	 *
	 * @access  public
	 * @since   1.2
	 */
	public $context = 'custom_integration';

	public function add_pending_referral( $payment_id = 0, $payment_data = array() ) {
		parent::add_pending_referral( $payment_id, $payment_data );

		// Add custom actions here. See the Affiliate_WP_EDD integration class for more info.
	}

}

new Custom_Integration;