CF 8.0 cfscript variable

Question

Pls check if this is a bug cos it seemed like the cfscript and main cfoutput shared the same variable:
Result : 5
Expeced Result: 1
<cfscript>
function  
valid4D(str){
if (len(str) neq 4) 
return false; 
if (Ucase(str) eq "XXXX") 
return false; 
for(i = 1; i lte 4; i = i + 1){c =
Mid(str, i, 1); 
if (Not Find(c, "0123456789xX")) 
return false;}
return true;}
</cfscript>
<cfloop 
from="1" to="1" index="i">
<cfif not #valid4D("5555")#>
<cfset err= 1>
</cfif>
<cfoutput>#i#</cfoutput></cfloop>

Answer 1

it seemed like the cfscript
and main cfoutput shared the same variable:
That is entirely possible. It does not look like you are VAR scoping your function variables. So when you declare your variables inside the function they are placed in the shared "variables" scope. The "variables" scope is accessible to the whole page, including your "main cfoutput".
You need to VAR scope all of your function local variables so they do not leak into the shared "variables" scope. 
function valid4D(str){
   VAR i = "";
   VAR c = "";
   .... etc ....