Form collection validation

TheForm.php

<?php
namespace Application\Form;

use Zend\Form\Form;
use Zend\InputFilter\InputFilterInterface;
use Zend\Form\Element\Collection;
use Application\Form\TranslationFieldset;

class TheForm extends Form
{
    const DESCRIPTIONS = "descriptions";
    const DESCRIPTION = "description";
    
    public function __construct(InputFilterInterface $inputFilter, $name = "TheForm")
    {
        parent::__construct($name);
        
        $this->initElements()
             ->setInputFilter($inputFilter);
    }
    
    protected function initElements()
    {
        $descriptionsElement = new Collection(self::DESCRIPTIONS);
        $descriptionsElement->setTargetElement(new TranslationFieldset(self::DESCRIPTION));
        $this->add($descriptionsElement);
        
        return $this;
    }
}

TheInputFilter.php

<?php
namespace Application\Form;

use Zend\InputFilter\InputFilter;
use Zend\InputFilter\Input;
use Zend\InputFilter\CollectionInputFilter;
use Zend\Filter\StringTrim;
use Zend\Filter\StripTags;

class TheInputFilter extends InputFilter
{
    public function __construct()
    {
        $this->initElements();
    }
    
    protected function initElements()
    {
        $descriptionsInputFilter = new InputFilter();
        
        $messageInput = new Input(TranslationFieldset::MESSAGE);
        $messageInput->getFilterChain()->attach(new StringTrim())
                                       ->attach(new StripTags());
        $descriptionsInputFilter->add($messageInput);
        
        $descriptionsContainerFilter = new CollectionInputFilter();
        $descriptionsContainerFilter->setInputFilter($descriptionsInputFilter)
                                    ->setIsRequired(false);

        $this->add($descriptionsContainerFilter, TheForm::DESCRIPTIONS);

        return $this;
    }
}

TheOtherInputFilter.php

<?php
namespace Application\Form;
 
use Zend\InputFilter\InputFilter;
use Zend\InputFilter\Input;
use Zend\InputFilter\CollectionInputFilter;
use Zend\Filter\StringTrim;
use Zend\Filter\StripTags;
 
class TheOtherInputFilter extends InputFilter
{
    public function __construct()
    {
        $this->initElements();
    }
    
    protected function initElements()
    {
        $descriptionsInputFilter = new InputFilter();
        
        $messageInput = new Input(TranslationFieldset::MESSAGE);
        $messageInput->getFilterChain()->attach(new StringTrim())
                                       ->attach(new StripTags());
        $descriptionsInputFilter->add($messageInput);
        
        $languageInput = new Input(TranslationFieldset::LANGUAGE);
        $languageInput->getFilterChain()->attach(new StringTrim())
                                        ->attach(new StripTags());
        $descriptionsInputFilter->add($languageInput);
        
        $descriptionsContainerFilter = new CollectionInputFilter();
        $descriptionsContainerFilter->setInputFilter($descriptionsInputFilter)
                                    ->setIsRequired(false);
 
        $this->add($descriptionsContainerFilter, TheForm::DESCRIPTIONS);
 
        return $this;
    }
}

TranslationFieldset.php

<?php
namespace Application\Form;

use Zend\Form\Fieldset;
use Zend\Form\Element\Select;
use Zend\Form\Element\Text;

class TranslationFieldset extends Fieldset
{
    const LANGUAGE = "language";
    const MESSAGE = "message";
    
    public function __construct($name)
    {
        parent::__construct($name);
        $this->initElements();
    }
    
    protected function initElements()
    {
        $languageElement = new Select(self::LANGUAGE);
        $languageElement->setValueOptions(
            array('es' => 'es', 'en' => 'en', 'fr' => 'fr', 'de' => 'de')
        );
        $this->add($languageElement);
        
        $messageElement = new Text(self::MESSAGE);
        $this->add($messageElement);
        
        return $this;
    }
}