Variable used without being declared

[SHAHRAM]

Hello,

I want to check if a global variable is set or not and set from within the function.

Can someone help me why am I getting "Variable used without being declared." for "$CHECK"?

#include <GUIConstantsEx.au3>

AutoItSetOption('MustDeclareVars', 0)

GUICreate("DUMMY", 532, 450, -1, -1)
GUISetState(@SW_SHOW)

chk()

While 1
    $nMsg = GUIGetMsg()
        Switch $nMsg
        Case $GUI_EVENT_CLOSE
            Exit
        EndSwitch
WEnd
    
Func chk()
    If IsDeclared($CHECK) Then
    EndIf   
EndFunc

[bo8ster]

The code you have is sorta redundant with your Opt command. Delectation of vars is forced by you, this it is checked before the script is executed. IsDeclared is run time, it won't get that far due to the compiler compiler (AU3Check).

[Tvern]

Check the parameters for IsDeclared.

"string representing name of the variable to be checked." means:

IsDeclared($CHECK) ;IsDeclared would expect $CHECK to contain a string representation of a variable to evaluate, rather than evaluate $CHECK itsself. 
;should be
IsDeclared("CHECK")