You can create a simple validator to do this:
class My_Validate_DateGreaterThanToday extends Zend_Validate_Abstract
{
const DATE_INVALID = 'dateInvalid';
protected $_messageTemplates = array(
self::DATE_INVALID => "'%value%' is not greater than or equal today"
);
public function isValid($value)
{
$this->_setValue($value);
$today = date('Y-m-d');
// expecting $value to be YYYY-MM-DD
if ($value < $today) {
$this->_error(self::DATE_INVALID);
return false;
}
return true;
}
}
And add it to the element:
$mockDate->addValidator(new My_Validate_DateGreaterThanToday());
You probably want to check the date with Zend_Date
for localization of dates and further benefits.
For creating custom validates, take a look at writing validators from Zend´s manual.