How do I show my custom validation error messages? (And other questions)

I'm trying to make a basic CRUD system.

I have a PostsController class:

Code:

<?php namespace App\Controllers;

use App\Models\Post;

class PostsController extends BaseController
{
        public function index()
        {
        $post = new Post();

                echo view('templates/header');
                echo view('posts/index', ['posts' => $post->findAll()]);
                echo view('templates/footer');
        }

    public function show($id)
    {
        $post = new Post();
        $result = $post->find($id);

        if( is_null($result) ) {
            throw \CodeIgniter\Exceptions\PageNotFoundException::forPageNotFound();
        }

                echo view('templates/header');
                echo view('posts/show', ['post' => $result ]);
                echo view('templates/footer');

    }

    public function create()
    {

        $postModel = new Post();
        $rules = $postModel->validationRules;

        if($this->request->getMethod() == 'post' && $this->validate($rules)) {
            $postModel->save([
                'title' => $this->request->getPost('title'),
                'content' => $this->request->getPost('content')
            ]);
        } else {
            echo view('templates/header', ['title' => 'Create a new post']);
            echo view('posts/create-form');
            echo view('templates/footer');
        }

    }

    public function edit($id)
    {
        $post = new Post();
        $result = $post->find($id);

        if( is_null($result) ) {
            throw \CodeIgniter\Exceptions\PageNotFoundException::forPageNotFound();
        }

                echo view('templates/header');
                echo view('posts/edit-form', ['post' => $result ]);
                echo view('templates/footer');
    }

    public function store()
    {
        $postModel = new Post();
        $rules = $postModel->validationRules;

        if($this->request->getMethod() == 'post' && $this->validate($rules)) {
            $postModel->save([
                'title' => $this->request->getPost('title'),
                'content' => $this->request->getPost('content')
            ]);
        } else {
            echo view('templates/header');
            echo view('posts/edit-form', ['validator' => $this->validator ]);
            echo view('templates/footer');
        }

        //return redirect('create-post');
    }

    public function update($id)
    {
        $postModel = new Post();
        $rules = $postModel->validationRules;
        $model = new Post();
        $post = $postModel->find($id);


        if( is_null($post) ) {
            throw \CodeIgniter\Exceptions\PageNotFoundException::forPageNotFound();
        }

        if($this->request->getMethod() == 'post' && $this->validate($rules)) {
            $postModel->update($id, [
                'title' => $this->request->getPost('title'),
                'content' => $this->request->getPost('content')
            ]);

            return redirect('home');

        } else {

            $this->edit($id);
        }

    }
}

and my Post model:

Code:

<?php namespace App\Models;

use CodeIgniter\Model;

class Post extends Model
{
    protected $table = 'posts';

    protected $primaryKey = 'id';

    protected $returnType = 'object';

    protected $allowedFields = ['title', 'content'];

    protected $validationRules    = [
        'title'     => 'required|alpha_numeric_space|min_length[3]',
        'content'        => 'required|min_length[10]',
    ];

    protected $validationMessages = [
        'title'        => [
            'required' => 'Sorry, this field must not be empty.',
        ]
    ];
}

The main issue I have is that the custom error messages are not displayed when there is an error. It seems like the defaults. How do I get CI to use them?

Also, in the PostsController class I use this a lot:

PHP Code:

        $rules = $postModel->validationRules;

        if($this->request->getMethod() == 'post' && $this->validate($rules)) { 


Is there a way for CI to just know that the rules have been defined and to use them rather than calling $this->validate() and having to inject the rules anyway. Why define them in the model in the first place if that is the case.

Additionally, there is a lot of code repetition in the PostsController class. Is that the CI way, or is there a way better way to keep things DRY?

Finally, is the main dev team happy to accept pull requests? I would really like to contribute to the project and wondered if that is possible? I have the same question for CI3. Are you looking for maintainers for that codebase? I could make another post for that though.