With id specified the function returns true if the player has the construction plan of the specified object. In this case iIndex and dwCategory are ignored. If id is 0, the function returns the indicated construction plan of the specified category.
if(GetPlrKnowledge(0,HUT1))
Message("Spieler %s kann Bambushütten bauen",0,GetPlayerName(0));
Displays a message if the first player has the construction plan for bamboo huts.
var def = GetPlrKnowledge( 0,0,4,C4D_Structure()) );
Message("Der fünfte Gebäude-Bauplan des Spielers ist %i",0,def);