从控制器到表单的zend传递变量

i'm developing an app and i'm trying to pass a variable from the controller to the form but without success. I need this variable for executing queries and populate fields of the form.

This is my code:

CONTROLLER:

$cod = $this->_getParam('cod');
        $form = new Application_Form_MylacForm($cod);

FORM:

public $_codanagrafica;
    protected $_codcircuito;

    public function __construct($codanagrafica = null, $param)
    {
        $this->_codcircuito = $param;
        echo $this->_codcircuito;
        $this->_codanagrafica = $codanagrafica;

        $this->init();
        $this->loadDefaultDecorators();
    }

With this code the variable _codcircuito is null.

How can i solve it?

Thank's

You are passing only one variable to form object:

$form = new Application_Form_MylacForm($cod);

And then you set _codcircuito with second argument, which is not passed:

$this->_codcircuito = $param;

$param is null in your case. Try:

$this->_codcircuito = $codanagrafica;

instead.