Question

how to turn off autocomplete in autogenerated form input element’s? in zend form’s?

Answer 1

Simply specify it as a property or as metadata on instantiation:

$foo = new Zend_Form_Element_Text('foo', array(
    'autocomplete' => 'off',
));

// or...
$form->addElement('text', 'foo', array(
    'autocomplete' => 'off',
));

// or...
$element->autocomplete = 'off';