The freeze URI option was added in 2.1, so you'll need to update
If you're looking for a way to define multiple links for a single url that may not be your best option as it basically forces a different URL for that resource - might as well just change its alias in 9/10 cases.
Could use a simple plugin like this triggering on the OnPageNotFound plugin:
$uri = $_SERVER['REQUEST_URI'];
$mapping = array(
'xyz.html' => 3,
'zyx.html' => 4,
'xzy.html' => 3
);
if (array_key_exists($uri, $mapping)) {
$modx->sendForward($mapping[$uri]);
}
Could generate the $mapping array from a resource TV value, get it from a custom table, a plaintext file somewhere on the server.... you name it.
Using modX.sendForward will make sure the link stays the same but that it serves a different resource.
Weblinks (and the Redirector extra) redirect to the other resource, and freeze_uri still makes the resource available at that link only.
☆ A M B ☆
☆ A M B ☆
☆ A M B ☆