I was able to use kmg's custom validator class successfully with Zend_Config_XML. just add the validator in the xml as normal. (of course php/zend needs to have read/required the custom class).
example code:
Code:
<elements>
<password>
<type>password</type>
<options>
<label>Password:</label>
<validators>
<strlen>
<validator>StringLength</validator>
<options>
<min>6</min>
</options>
</strlen>
</validators>
<required>true</required>
</options>
</password>
<passwordcheck>
<type>password</type>
<options>
<label>Retype password:</label>
<validators>
<comparetofield>
<validator>CompareToField</validator>
<options>
<field>password</field>
</options>
</comparetofield>
</validators>
<required>true</required>
</options>
</passwordcheck>
</elements>
thanks kmg.
-eathaiku