NSIS push, pop and URLEncode

[theChaser]

I'm trying to encode with URLEncode a strings in NSIS. I'm using a NSIS plugin called URLEncode. The problem is that I try encode 2 vars, but the first encoded var lost the value after I encoded the second var.

PHP Code:

Push "${AFF_NAME}"
Call URLEncode
Pop $3
; // at this point the messagebox show the result good.
MessageBox MB_OK $3

ReadRegStr $0 HKLM "SOFTWARE\Microsoft\Windows NT\CurrentVersion" "ProductName"
Push $0
Call URLEncode
Pop $0
; // now after second var encoded the result of first var $3 lost the value
MessageBox MB_OK $3 


Please Help I'm very new using NSIS and I dont know how do it good. I searching info but without success.

Very thanks !