How do I add callback validator with addElement in zend form?

Question

I'm trying to create a simple Zend form using pm_Form_Simple class. I need a callback validator with its addElement method. Here's what I did.

$form = new pm_Form_Simple();
$form->addElement('text','my_number',
                 array('label'=>'Your number',
                'validators'=>array(
                                array('name'=>'Callback',false,'
                                options'=>array('messages'=>'Invalid number',
                               'callback'=>function($value,$context=array()){
                                                if($value < 0){ 
                                                     return false;
                                                }else{ 
                                                    return true;
                                                }    
                                         },
                                 ))
                   )));

This gives me an error when submitting the form

Missing argument 1 for CommonPanel_Validate_Callback::__construct()

I have tried this structure also

 array(
      new \Zend\Validator\Callback(
      array(
     'messages' => array(\Zend\Validator\Callback::INVALID_VALUE => 'Invalid number'),
      'callback' => function($value){
                        if($value < 0){ 
                           return false;
                        }else{ 
                          return true;
                        }  
                    }
   )))

This gave me an error include_once(Zend/Validator/Callback.php): failed to open stream: No such file or directory

I don't see Zend/Validator in my zend installation,so I changed it to zend/Validate

This time the error was Class 'Zend\Validate\Callback' not found

I know there exists LessThan & GreaterThan validators, but can anyone kindly help/guide me on how to add callback validator with addElement function ?