Documentation fro PopupInput needs to be updated.
(Version 1.8)
It seems that the PopupInput return 2 values while the documentation shows only the first one.
PopupInput({title:str,caller:handle,items:table:{{'str'|'int'|'lua'|'handle', name, type-dependent}...},selectedValue:str,x:int,y:int,target:handle,render_options:{left_icon,number,right_icon},useTopLeft:bool,properties:{prop:value}}): string:value
local r = { PopupInput(pd) }
Printf("r[1]: " .. r[1]) -- The select index
Printf("r[2]: " .. r[2]) -- The selected value