I would most likely leave it requiredinstalled by default and use NotEmptyvalidator instead.
$this->addElement('text', 'age', array(
'label'=>'Age',
'maxlength'=>2,
'class'=>'age',
'filters'=>array('StringTrim'),
'validators'=>array(
array(
'validator'=>'Int',
'options'=>array(
'messages'=>'Age must be a number.'
)
),
array(
'validator'=>'NotEmpty',
'options'=>array(
'messages'=>'Please enter your age.'
)
),
array(
'validator'=>'between',
'options'=>array(
'min'=>8,
'max'=>10,
'messages'=>array(
Zend_Validate_Between::NOT_BETWEEN => 'Your age must be between %min% to %max%.'
)
)
)
),
'decorators'=>array(
'ViewHelper',
'Errors',
array(array('control'=>'HtmlTag'), array('tag'=>'div', 'class'=>'fieldcontrol')),
array('Label', array('tag'=>'div', 'class'=>'age')),
array(array('row'=>'HtmlTag'), array('tag' => 'div', 'class'=>'row')),
),
));
NotEmpty() , isRequired(), , isRequired() , Zend_Form_Element. .