By default, some form elements (such as Zend_Form_Element_MultiCheckbox and so on) register an InArray validator which validates against the array keys of registered options. This validator used case sensitive compaision. What is the simplest what to make case insensitive? The only solution that occurs to me now looks something like this. Turn off this validator:
$element->setRegisterInArrayValidator(false);
Create new validator that will make case insensitive comparision and add this validation for the element. Is this the only way to solve this problem? It seems it would be nice if there is a standard way to make inArray validator to make case insensitive comparision.