Oh, geez, is this one embarrassing.
> // grab the points layer and tweak it
> $points_datasource = $TEMPDIR.'/points_'.$_REQUEST['sessionid'].'.shp';
> $layer = $map->getLayerByName('points');
> $layer->set('data',$tracks_datasource);
> $layer->set('status',MS_ON);I was loading $tracks_datasource instead of $points_datasource. Naturally, reading the wrong shapefile was not helping. As the saying goes: "User error. Replace user and reboot." Sorry to both y'all. :)
