$api_url = ""; // << ---- Your Active Campaign API URL should go in here
$api_key = ""; // << ---- Your Active Campaign API Key should go in here
define("ACTIVECAMPAIGN_URL", $api_url);
define("ACTIVECAMPAIGN_API_KEY", $api_key);
require_once("../link/to/includes/ActiveCampaign.class.php"); // << ---- path to the included Active Campaign API file: ActiveCampaign.class.php
$ac = new ActiveCampaign(ACTIVECAMPAIGN_URL, ACTIVECAMPAIGN_API_KEY);