Create and Manage Affiliates based on membership level when using AffiliateWP and Paid Memberships Pro

my_pmpro_affiliatewp_after_change_membership_level.php

<?php
/*
  Creates an affiliate for new members of Level ID 1. 
  Updates affiliate status if the affiliate already exists.
  Sets affilaite status to 'inactive' if membership of Level ID 1 is cancelled (includes expiration).
  
  Add this code to a custom plugin.
*/
function my_pmpro_affiliatewp_after_change_membership_level( $level_id, $user_id, $cancel_level ) {	
	//make sure affiliatewp is active
	if(!function_exists('affwp_is_affiliate'))
		return;
	
	if($level_id == 1) {
		//New member of level 1. Set up the Affiliate
		if( affwp_is_affiliate( $user_id ) ) {
			$affiliate_id = affwp_get_affiliate_id( $user_id );
			//Affiliate already exists. Update Affiliate status to 'active'.
			affwp_update_affiliate( array( 'affiliate_id' => $affiliate_id, 'status' => 'active' ) );
		} else {
			//Affiliate does not exist. Create the Affiliate.
			affwp_add_affiliate( array( 'user_id' => $user_id, 'status' => 'active' ) );
		}
	} 
	if($cancel_level == 1) {
		//User is cancelling or membership is expired.
		if( affwp_is_affiliate( $user_id ) ) {
			$affiliate_id = affwp_get_affiliate_id( $user_id );
			//Affiliate exists. Update Affiliate status to 'inactive'.
			affwp_update_affiliate( array( 'affiliate_id' => $affiliate_id, 'status' => 'inactive' ) );
		}
	}
}
add_action('pmpro_after_change_membership_level', 'my_pmpro_affiliatewp_after_change_membership_level', 10, 3);

This recipe is included in the blog post on "Create and Manage Affiliates by Membership Level Using AffiliateWP" at Paid Memberships Pro here: https://www.paidmembershipspro.com/create-manage-affiliates-membership-level-using-affiliatewp/