Adding new fields to Article Form

Module.php

<?php
    public function onBootstrap(MvcEvent $e)
    {
        $sharedManager = $e->getApplication()->getEventManager()->getSharedManager();
        $sharedManager->attach('LibraArticle\Controller\ArticleController', 'dispatch', function($e) {
            // Add current article to layout
            $controller = $e->getTarget();
            $controller->getEventManager()->attach('view', function($e) {
                $article = $e->getParam('article');
                $controller = $e->getTarget();
                $controller->layout()->setVariable('article', $article);
            });
        }, 100);
 

        $sharedManager->attach('LibraArticle\Controller\AdminArticleController', 'dispatch', function($e) {
            $controller = $e->getTarget();

            $controller->getEventManager()->attach('save.post', function($e) {
                $article = $e->getParam('article');
                $data = $e->getParam('data');
                $article->setParam('heading2', $data['heading2']);

                // Return true to save changes to DB
                return true;
            });

            $controller->getEventManager()->attach('get', function($e) {
                $article = $e->getParam('article');
                $data = $e->getParam('data');
                $data['heading2'] = $article->getParam('heading2');
            });

            $controller->getEventManager()->attach('form.init', function($e) {
                $form = $e->getParam('form');

                // Add specefic inputs
                $form->getInputFilter()->add(array(
                    'name'       => 'heading2',
                    'required'   => false,
                ));

                $form->add(array(
                    'type' => 'Text',
                    'name' => 'heading2',
                    'options' => array(
                        'label' => 'Heading 2',
                    ),
                ));

                return null;
            });
        }, 100);
    }