Coldfusion和会话变量未设置

Question

I have a survey form with 5 ques, there is one question on each page and user clicks through them with next button on the page. Now, the user is not logged in, I want to set a session variable only when the user takes the first ques on form and clicks next. But I am getting userid not defined in session for the line 2. I am not really sure what I am doing wrong here. Can anyone suggest if they see what is going on. I don't want to be creating multiple userids every time he hits next button. Thanks

<cfif structKeyExists(FORM, "user_mode") and form.user_mode EQ "next">  

<cfif NOT ( StructKeyExists(session,userid) )> 
<cfquery name="insertuser" datasource="#application.datasource#">
         INSERT INTO survey_user(ip_address)
            VALUES (<cfqueryparam cfsqltype="cf_sql_varchar" value="#CGI.REMOTE_ADDR#" />)
        </cfquery>
</cfif>
</cfif>

Answer 1

StructKeyExists(session,userid)

should be:

structKeyExists( session, 'userid' )

Note the quotes. Without them it's looking for the variable "userid" rather than the key name "userid".