Rob Allen has posted
a quick tip of how to use the Zend_Form component of the
Zend Framework to correctly render XHTML compliant output.
When you render a Zend_Form, the elements will render to HTML compliance rather than XHTML compliance, even if you have < ?php echo $this->doctype('XHTML1_STRICT');?> at the top of your layout script. Practically, this means that all the input elements do not end in "/>". To resolve this, you need to call the doctype() view helper prior to rendering your form.
He includes an
example of the doctype call (on a view object) to tell the script to output in the "XHTML1_TRANSITIONAL" format.
Rob Allen's Blog: Top Tip: XHTML with Zend Form Elements - Read More... 
