Point the Authorize.net integration to a different end point (e.g. to use an Authorize.net mirror API)

my_pmpro_authorizenet_post_url.php

<?php
/*
 * Point the Authorize.net integration for PMPro to a different end point (e.g. to use an Authorize.net mirror API)
 *
 */
function my_pmpro_authorizenet_post_url( $url, $environment ) {
    if ($environment == "sandbox") {
        $url = 'https://domain.com/path-to-the-sandbox-endpoint/';
    } else {
        $url = 'https://domain.com/path-to-the-live-endpoint/';
    }
    return $url;
}
add_filter( 'pmpro_authorizenet_post_url', 'my_pmpro_authorizenet_post_url', 10, 2 );

This recipe is included in the blog post on "Point the Authorize.net integration to a different end point." at Paid Memberships Pro here: https://www.paidmembershipspro.com/point-the-authorize-net-integration-to-a-different-end-point/