Keep Referral Var on Redirect

keep-referral-var-on-redirect.php

<?php
/**
 * Keeps the referral var when wp_redirect is used.
 */
function affwpsupport_keep_referral_var_on_wp_redirect( $location, $status ) {
	if ( function_exists( 'affiliate_wp' ) ) {
		// Get the referral variable being used in AffiliateWP.
		$referral_var = affiliate_wp()->tracking->get_referral_var();
		if ( $_GET[ $referral_var ] ) {
			// Append the referral variable and value to the URL after the redirect.
			$location = add_query_arg( $referral_var, $_GET[ $referral_var ], $location );
		}
	}
	return $location;
}
add_filter( 'wp_redirect', 'affwpsupport_keep_referral_var_on_wp_redirect', 10, 2 );