A normal grid connector expects that the target table has some autogenerated ID field, but in some cases data needs to be loaded and saved from a database table which doesn't have such an autofilled ID.
A normal grid connector can be used for data loading from such tables, but won't be able to save the data back. KeyGridConnector can resolve such a problem (use it instead of GridConnector):
$grid = new KeyGridConnector($res); $grid->render_table("mytable","name","name,address,phone");
So, there are two differences from the normal GridConnector: