ZF2: Extend a Form View Helper and make it available from view - zend-framework2

Question

I need to render a Multicheck options like this:
<input type="checkbox" name="avoid_transport[voiture]" value="1">
<input type="checkbox" name="avoid_transport[plane]" value="1">
...
but I achieve to render like:
<input type="checkbox" name="avoid_transport[]" value="voiture">
<input type="checkbox" name="avoid_transport[]" value="plane">
Following appreciate guide, I need to create a custom view extending the Multicheck View Helper, but I am having problems.
This is my extended class:
namespace Multicity\Helper;
use Zend\Form\Element\MultiCheckbox as MultiCheckboxElement;
class FormMultiCheckboxArray extends MultiCheckboxElement
{
public function render()
{
/* do my own render here or render_options */
return;
}
}
I make it available through the view helper manager:
// module.config.php
'view_helper' => array(
'invokables' => array(
'formMultiCheckboxArray' => 'Multicity\Helper\FormMultiCheckboxArray'
)
),
I create the form element using the extended class:
$this->add(array(
'type' => 'Multicity\Helper\FormMultiCheckboxArray',
'name' => 'avoid_transport',
'options' => array(
'value_options' => array(
'0' => 'voiture',
'1' => 'avion',
),
),
'attributes' => array(
'value' => 1,
)
));
and at the view:
<?php echo $this->formMultiCheckboxArray($form->get('avoid_transport')); ?>
And I get this error message:
Zend\View\HelperPluginManager::get was unable to fetch or create an instance for formMultiCheckboxArray
Please, anybody could help me to figure out what I am missing?
I will appreciate any kind of guide. Thank for your time.
Regards.