PHPR 5.2 b.4689 will not retain the value set when trying to modify auto-increment field.
It will allow the selection of a field to be set as key but upon exiting the modify table form, the changes made are lost and reset to original values.
Although it is possible to modify the table and set an index and primary key auto-increment value to the field via phpmyadmin. Any changes made will be reflected in the PHPR >> datasource table page upon synchronization.
Vince