Passing data between pages

Silvestro wrote: Hello, I have two pages, form.cfm, and validation.cfm. I wish to check in validation the values submitted by form. In case of error or wrong values, I'd redirect the user back to form, with wrong fields highlighted. Now, I don't know how to pass these values between the pages. If I put them into session, the user will keep them for a longer time than expected. I could destroy those values once values are validated as ok, but am unwilling to write/test/check too much. But since sessions rely on cookies, am I to write a page for cookies disabled users, and one for javascript disabled users? I could put validation and form on the same page, but don't want either to make my page a mess. Any suggestion, if any?

You could use session variables and, instead of bothering about deleting them, simply update them dynamically. The following pseudocode is more or less similar to Steve's approach.

form.cfm

========

<cfif isDefined("session.isFormSubmitted") and session.isFormSubmitted>

<div>
<!--- loop through the fields, and print a validation message where the field's validation status is 0--->
<cfloop collection="#session.status#" item="field">
<cfif session.status[field] is 0>
<cfoutput>
<p>#field#: #session.message[field]#</p>
</cfoutput>
</cfif>
</cfloop>
</div>

<!--- (re-)populate fields with the values stored in session scope --->
<cfform action="validation.cfm">
Field 1: <cfinput type="text" name="field_1" value="#session.value.field_1#"><br>
Field 2: <cfinput type="text" name="field_2" value="#session.value.field_2#"><br>
Field 3: <cfinput type="text" name="field_3" value="#session.value.field_3#"><br>
<cfinput type="submit" name="sbmt" value="Send">
</cfform>

<!--- reset the value --->
<cfset session.isFormSubmitted = False>

<cfelse>

<cfform action="validation.cfm">
Field 1: <cfinput type="text" name="field_1" required="true" message="You must enter a value for field 1."><br>
Field 2: <cfinput type="text" name="field_2" required="true" message="You must enter a value for field 2."><br>
Field 3: <cfinput type="text" name="field_3" required="true" message="You must enter a value for field 3."><br>
<cfinput type="submit" name="sbmt" value="Send">
</cfform>

</cfif>

validation.cfm

============

<cfset formValidationStatus = 1>
<cfset session.isFormSubmitted = True>

<cfset session.value.field_1="">
<cfset session.value.field_2="">
<cfset session.value.field_3="">
<cfset session.status.field_1=0>
<cfset session.status.field_2=0>
<cfset session.status.field_3=0>
<cfset session.message.field_1="">
<cfset session.message.field_2="">
<cfset session.message.field_3="">

<cfif isDefined("form.sbmt")><!--- then form submitted --->
    <!--- store the values in session scope --->
    <cfset session.value.field_1=form.field_1>
    <cfset session.value.field_2=form.field_2>
    <cfset session.value.field_3=form.field_3>
   
    <!--- validate for each and every field. Set the status to 1 if validation succeeds, to 0 if it fails --->
    <!--- I'll illustrate with just field_1. Suppose it represents a year between 1900 and 2020. --->
    <cfif (len(trim(form.field_1)) EQ 4) and (isNumeric(form.field_1)) and (form.field_1 GTE 1900 and form.field_1 LTE 2020)>
        <cfset session.status.field_1=1>
    <cfelse>
        <!--- If status of a field is 0, then include the validation message to the seesion struct --->
        <cfset session.message.field_1="Field 1 must be a year between 1900 and 2020.">
    </cfif>
   
    <!--- Loop through all the status values. If at least one of the fields fails to validate, then set formValidationStatus to 0, meaning a return to the form page --->
    <cfloop collection="#session.status#" item="field">
        <cfif session.status[field] EQ 0>
            <cfset formValidationStatus = 0>
            <cfbreak>
        </cfif>
    </cfloop>
</cfif>

<cfif formValidationStatus EQ 0>
    <cflocation url="form.cfm">
<cfelse><!--- all submitted fields valid --->
<!--- proceed with business logic --->
</cfif>

I wrote a Form Validation and Flow -- One Technique tutorial several years back that I think will point you in the right direction. This tutorial focuses strictly on server-side validation which is a must whereas most of the responses here focus on client-side validation. You really need both -- one prevents hackers from posting cross-site scripting (XSS) and SQL injection code, the other provides much more user friendly form handling with instant feedback to the user.

It sounds to me like what you want to use is just a basic HTML form. I'd suggest reading up on those before you go delving into the CF side.