2006-11-16 Checking form fields

When you're creating dynamic web pages with forms on them, you'll probably not forget to validate the values that the user sent in a text box. Will you check which values come in from a selection box?

You probably wouldn't. After all, the user can't edit the values. Novell certainly doesn't. Novell has a piece of software called Webmail, so users can read their mail using their favorite browser instead of the Novell client.

That's useful. Using Webmail, users can also define server side e-mail rules, for instance to automatically move incoming e-mails from an mailing list to a specific folder. Most mailinglists put a specific piece of text in the subject, but others can be recognized by the e-mail address of the list, which is in the To: or CC: field.

Except... with webmail, the only fields you can enter, are the "From", "To", "Subject" and "Message" (body) fields. This is a non-editable select box.

Except it's editable. This can be done with any programmable web client, such as the libwww-perl module. Luckily, Firefox has the webdeveloper extension, which can turn select fields into text fields.

Novell's Webmail application luckily doesn't validate these fields. So all of a sudden, we have an extra feature where we can sort out e-mails according to the contents of the CC: field.

Useful when you're on a dating site and you're not looking for the (boring) choices of Male or Female, but -- say -- Muppet.

On a serious note, your framework for web development should provide automatic checks for this. For instance, PHP's PEAR classes contain the HTML_QuickForm class which programmatically can build HTML forms and (amongst hundreds of other features) nicely checks whether the entered values don't deviate from the possible selections.