Piggybacking @ChuckMac , , , WordPress API- , WordPress . WP init hook, , "" $_REQUEST. plugins_loaded .
add_action( 'init', 'so_26193801_event_listener' );
function so_26193801_event_listener(){
if(isset($_REQUEST['Action'])){
$Action = $_REQUEST['Action'];
switch($Action){
case "ValidateSubscription":
$Subscriptions = WC_Subscriptions_Manager::get_all_users_subscriptions();
print_r($Subscriptions);
break;
default:
echo "invalid action";
}
} else {
echo "no action specified";
}
}