Facebook pmd system: Given URL is not allowed by the Application configuration

We are developing a Facebook PMD system,but when we upload the link through API,we get this error:'Given URL is not allowed by the Application configuration.: One or more of the given URLs is not allowed by the App's settings. It must match the Website URL or Canvas URL, or the domain must be a subdomain of one of the App's domains' . We did what people say: add link in Site URL and the issue was solved. But since we are a PMD system,it should allow different users to add different links in our system.But 'Site URL' can only add one link. What should we do?