A table function calls FNC_GetPhase before doing anything else.
For a table function that is passed in a variable set of input arguments (where the mode is TBL_MODE_VARY) and needs to know when it is being passed in the last logical, or qualified, row on an AMP, the best practice is to use FNC_GetPhaseEx instead of FNC_GetPhase. For details, see FNC_GetPhaseEx.