[pmwiki-users] Advice on using captcha with an email form?

[Heikki Vuolteenaho]

Hi all,

We are running a website using PmWiki. It has some feedback forms for 
users, which have unfortunately been found by spammers. I'm getting
quite annoyed by the amount of spam we are receiving...

I recently noticed a captcha recipe in the pmwiki cookbook:
http://www.pmwiki.org/wiki/Cookbook/Captcha

Surfing a bit more, I found a mailform recipe:
http://www.pmwiki.org/pmform/PmForm/MailForm

I thought I could easily combine these two to replace our current mail 
forms with a spammer-resistant version. I think our current forms are 
using the BuildForms recipe and some custom php code.

I managed to create a sample mail form with the captcha image showing, 
but could not quite finish the task. Editing the Site.PmFormTemplates, I 
could easily use the following line to require some fields to be filled 
before the form can be sent:

(:template require from errmsg="$[Missing 'from' address]" :)

But how can I verify that the captcha was input correctly? Or if this is 
not currently possible, do you have suggestions on how I could easily 
create a captcha-protected mailform?

Thanks in advance!

-Heikki-


P.S. I'm quite new to PmWiki (and PHP), so please try to be verbose when 
answering :)