How do I protect my software with the license client?

1. Open License > Licenses and click Download Client. The file already points at your own site.
2. Add it to your software and check the customer's key before anything else runs:

require 'LicenseClient.php';

$license = new LicenseClient('THE-CUSTOMERS-KEY');

if (! $license->isValid()) {
    die('License error: ' . $license->getMessage());
}

The first check locks the key to the domain, IP address and directory it ran from. The result is cached for 12 hours, and a recent good answer keeps working for up to 72 hours if your site cannot be reached.

If a customer moves to a new server, they clear the lock from their client area (when the product has Allow Reissue on) or you use Reset lock on the license.

More: Sell licenses for your own software.