Blog Tutorial - Adding a layer¶

Create a Post Model¶

The Model class is the bread and butter of CakePHP applications. By creating a CakePHP model that will interact with our database, we’ll have the foundation in place needed to do our view, add, edit, and delete operations later.

CakePHP’s model class files go in /app/Model, and the file we’ll be creating will be saved to /app/Model/Post.php. The completed file should look like this:

class Post extends AppModel {
}

Naming conventions are very important in CakePHP. By naming our model Post, CakePHP can automatically infer that this model will be used in the PostsController, and will be tied to a database table called posts.

For more on models, such as table prefixes, callbacks, and validation, check out the Models chapter of the Manual.

Create a Posts Controller¶

Next, we’ll create a controller for our posts. The controller is where all the controlling logic for post interaction will happen. In a nutshell, it’s the place where you play with the models and get post-related work done. We’ll place this new controller in a file called PostsController.php inside the /app/Controller directory. Here’s what the basic controller should look like:

class PostsController extends AppController {
    public $helpers = array('Html', 'Form');
}

Now, let’s add an action to our controller. Actions often represent a single function or interface in an application. For example, when users request www.example.com/posts/index (which is the same as www.example.com/posts/), they might expect to see a listing of posts. The code for that action would look something like this:

class PostsController extends AppController {
    public $helpers = array('Html', 'Form');

    public function index() {
        $this->set('posts', $this->Post->find('all'));
    }
}

By defining function index() in our PostsController, users can access the logic there by requesting www.example.com/posts/index. Similarly, if we were to define a function called foobar(), users would be able to access that at www.example.com/posts/foobar.

The single instruction in the action uses set() to pass data from the controller to the view (which we’ll create next). The line sets the view variable called ‘posts’ equal to the return value of the find('all') method of the Post model. Our Post model is automatically available at $this->Post because we’ve followed CakePHP’s naming conventions.

To learn more about CakePHP’s controllers, check out the Controllers chapter.

Creating Post Views¶

Now that we have our data flowing to our model, and our application logic and flow defined by our controller, let’s create a view for the index action we created above.

CakePHP views are just presentation-flavored fragments that fit inside an application’s layout. For most applications, they’re HTML mixed with PHP, but they may end up as XML, CSV, or even binary data.

A layout is presentation code that is wrapped around a view. Multiple layouts can be defined, and you can switch between them, but for now, let’s just use the default.

Remember how in the last section we assigned the ‘posts’ variable to the view using the set() method? That would pass data to the view that would look something like this:

// print_r($posts) output:

Array
(
    [0] => Array
        (
            [Post] => Array
                (
                    [id] => 1
                    [title] => The title
                    [body] => This is the post body.
                    [created] => 2008-02-13 18:34:55
                    [modified] =>
                )
        )
    [1] => Array
        (
            [Post] => Array
                (
                    [id] => 2
                    [title] => A title once again
                    [body] => And the post body follows.
                    [created] => 2008-02-13 18:34:56
                    [modified] =>
                )
        )
    [2] => Array
        (
            [Post] => Array
                (
                    [id] => 3
                    [title] => Title strikes back
                    [body] => This is really exciting! Not.
                    [created] => 2008-02-13 18:34:57
                    [modified] =>
                )
        )
)

CakePHP’s view files are stored in /app/View inside a folder named after the controller to which they correspond. (We’ll have to create a folder named ‘Posts’ in this case.) To format this post data into a nice table, our view code might look something like this

<!-- File: /app/View/Posts/index.ctp -->

<h1>Blog posts</h1>
<table>
    <tr>
        <th>Id</th>
        <th>Title</th>
        <th>Created</th>
    </tr>

    <!-- Here is where we loop through our $posts array, printing out post info -->

    <?php foreach ($posts as $post): ?>
    <tr>
        <td><?php echo $post['Post']['id']; ?></td>
        <td>
            <?php echo $this->Html->link($post['Post']['title'],
array('controller' => 'posts', 'action' => 'view', $post['Post']['id'])); ?>
        </td>
        <td><?php echo $post['Post']['created']; ?></td>
    </tr>
    <?php endforeach; ?>
    <?php unset($post); ?>
</table>

You might have noticed the use of an object called $this->Html. This is an instance of the CakePHP HtmlHelper class. CakePHP comes with a set of view helpers that make things like linking, form output, JavaScript and AJAX a snap. You can learn more about how to use them in Helpers, but what’s important to note here is that the link() method will generate an HTML link with the given title (the first parameter) and URL (the second parameter).

When specifying URLs in CakePHP, it is recommended that you use the array format. This is explained in more detail in the section on Routes. Using the array format for URLs allows you to take advantage of CakePHP’s reverse routing capabilities. You can also specify URLs relative to the base of the application in the form of /controller/action/param1/param2.

At this point, you should be able to point your browser to http://www.example.com/posts/index. You should see your view, correctly formatted with the title and table listing of the posts.

If you happened to have clicked on one of the links we created in this view (which link a post’s title to a URL /posts/view/some_id), you were probably informed by CakePHP that the action hadn’t yet been defined. If you were not so informed, either something has gone wrong, or you actually did define it already, in which case you are very sneaky. Otherwise, we’ll create it in the PostsController now:

// File: /app/Controller/PostsController.php
class PostsController extends AppController {
    public $helpers = array('Html', 'Form');

    public function index() {
         $this->set('posts', $this->Post->find('all'));
    }

    public function view($id = null) {
        if (!$id) {
            throw new NotFoundException(__('Invalid post'));
        }

        $post = $this->Post->findById($id);
        if (!$post) {
            throw new NotFoundException(__('Invalid post'));
        }
        $this->set('post', $post);
    }
}

The set() call should look familiar. Notice we’re using findById() rather than find('all') because we only want a single post’s information.

Notice that our view action takes a parameter: the ID of the post we’d like to see. This parameter is handed to the action through the requested URL. If a user requests /posts/view/3, then the value ‘3’ is passed as $id.

We also do a bit of error checking to ensure that a user is actually accessing a record. If a user requests /posts/view, we will throw a NotFoundException and let the CakePHP ErrorHandler take over. We also perform a similar check to make sure the user has accessed a record that exists.

Now let’s create the view for our new ‘view’ action and place it in /app/View/Posts/view.ctp

<!-- File: /app/View/Posts/view.ctp -->

<h1><?php echo h($post['Post']['title']); ?></h1>

<p><small>Created: <?php echo $post['Post']['created']; ?></small></p>

<p><?php echo h($post['Post']['body']); ?></p>

Verify that this is working by trying the links at /posts/index or manually requesting a post by accessing /posts/view/1.

Adding Posts¶

Reading from the database and showing us the posts is a great start, but let’s allow for adding new posts.

First, start by creating an add() action in the PostsController:

class PostsController extends AppController {
    public $helpers = array('Html', 'Form', 'Flash');
    public $components = array('Flash');

    public function index() {
        $this->set('posts', $this->Post->find('all'));
    }

    public function view($id) {
        if (!$id) {
            throw new NotFoundException(__('Invalid post'));
        }

        $post = $this->Post->findById($id);
        if (!$post) {
            throw new NotFoundException(__('Invalid post'));
        }
        $this->set('post', $post);
    }

    public function add() {
        if ($this->request->is('post')) {
            $this->Post->create();
            if ($this->Post->save($this->request->data)) {
                $this->Flash->success(__('Your post has been saved.'));
                return $this->redirect(array('action' => 'index'));
            }
            $this->Flash->error(__('Unable to add your post.'));
        }
    }
}

Here’s what the add() action does: if the HTTP method of the request was POST, it tries to save the data using the Post model. If for some reason it doesn’t save, it just renders the view. This gives us a chance to show the user validation errors or other warnings.

Every CakePHP request includes a CakeRequest object which is accessible using $this->request. The request object contains useful information regarding the request that was just received, and can be used to control the flow of your application. In this case, we use the CakeRequest::is() method to check that the request is a HTTP POST request.

When a user uses a form to POST data to your application, that information is available in $this->request->data. You can use the pr() or debug() functions to print it out if you want to see what it looks like.

We use the FlashComponent’s FlashComponent::success() method to set a message to a session variable to be displayed on the page after redirection. In the layout we have FlashHelper::render() which displays the message and clears the corresponding session variable. The controller’s Controller::redirect function redirects to another URL. The param array('action' => 'index') translates to URL /posts (that is, the index action of the posts controller). You can refer to Router::url() function on the API to see the formats in which you can specify a URL for various CakePHP functions.

Calling the save() method will check for validation errors and abort the save if any occur. We’ll discuss how those errors are handled in the following sections.

We call the create() method first in order to reset the model state for saving new information. It does not actually create a record in the database, but clears Model::$id and sets Model::$data based on your database field defaults.

Data Validation¶

CakePHP goes a long way toward taking the monotony out of form input validation. Everyone hates coding up endless forms and their validation routines. CakePHP makes it easier and faster.

To take advantage of the validation features, you’ll need to use CakePHP’s FormHelper in your views. The FormHelper is available by default to all views at $this->Form.

Here’s our add view:

<!-- File: /app/View/Posts/add.ctp -->

<h1>Add Post</h1>
<?php
echo $this->Form->create('Post');
echo $this->Form->input('title');
echo $this->Form->input('body', array('rows' => '3'));
echo $this->Form->end('Save Post');
?>

We use the FormHelper to generate the opening tag for an HTML form. Here’s the HTML that $this->Form->create() generates:

<form id="PostAddForm" method="post" action="/posts/add">

If create() is called with no parameters supplied, it assumes you are building a form that submits via POST to the current controller’s add() action (or edit() action when id is included in the form data).

The $this->Form->input() method is used to create form elements of the same name. The first parameter tells CakePHP which field they correspond to, and the second parameter allows you to specify a wide array of options - in this case, the number of rows for the textarea. There’s a bit of introspection and automagic here: input() will output different form elements based on the model field specified.

The $this->Form->end() call generates a submit button and ends the form. If a string is supplied as the first parameter to end(), the FormHelper outputs a submit button named accordingly along with the closing form tag. Again, refer to Helpers for more on helpers.

Now let’s go back and update our /app/View/Posts/index.ctp view to include a new “Add Post” link. Before the <table>, add the following line:

<?php echo $this->Html->link(
    'Add Post',
    array('controller' => 'posts', 'action' => 'add')
); ?>

You may be wondering: how do I tell CakePHP about my validation requirements? Validation rules are defined in the model. Let’s look back at our Post model and make a few adjustments:

class Post extends AppModel {
    public $validate = array(
        'title' => array(
            'rule' => 'notBlank'
        ),
        'body' => array(
            'rule' => 'notBlank'
        )
    );
}

The $validate array tells CakePHP how to validate your data when the save() method is called. Here, I’ve specified that both the body and title fields must not be empty. CakePHP’s validation engine is strong, with a number of pre-built rules (credit card numbers, email addresses, etc.) and flexibility for adding your own validation rules. For more information, check the Data Validation.

Now that you have your validation rules in place, use the app to try to add a post with an empty title or body to see how it works. Since we’ve used the FormHelper::input() method of the FormHelper to create our form elements, our validation error messages will be shown automatically.

Editing Posts¶

Post editing: here we go. You’re a CakePHP pro by now, so you should have picked up a pattern. Make the action, then the view. Here’s what the edit() action of the PostsController would look like:

public function edit($id = null) {
    if (!$id) {
        throw new NotFoundException(__('Invalid post'));
    }

    $post = $this->Post->findById($id);
    if (!$post) {
        throw new NotFoundException(__('Invalid post'));
    }

    if ($this->request->is(array('post', 'put'))) {
        $this->Post->id = $id;
        if ($this->Post->save($this->request->data)) {
            $this->Flash->success(__('Your post has been updated.'));
            return $this->redirect(array('action' => 'index'));
        }
        $this->Flash->error(__('Unable to update your post.'));
    }

    if (!$this->request->data) {
        $this->request->data = $post;
    }
}

This action first ensures that the user has tried to access an existing record. If they haven’t passed in an $id parameter, or the post does not exist, we throw a NotFoundException for the CakePHP ErrorHandler to take care of.

Next the action checks whether the request is either a POST or a PUT request. If it is, then we use the POST data to update our Post record, or kick back and show the user validation errors.

If there is no data set to $this->request->data, we simply set it to the previously retrieved post.

The edit view might look something like this:

<!-- File: /app/View/Posts/edit.ctp -->

<h1>Edit Post</h1>
<?php
echo $this->Form->create('Post');
echo $this->Form->input('title');
echo $this->Form->input('body', array('rows' => '3'));
echo $this->Form->input('id', array('type' => 'hidden'));
echo $this->Form->end('Save Post');
?>

This view outputs the edit form (with the values populated), along with any necessary validation error messages.

One thing to note here: CakePHP will assume that you are editing a model if the ‘id’ field is present in the data array. If no ‘id’ is present (look back at our add view), CakePHP will assume that you are inserting a new model when save() is called.

You can now update your index view with links to edit specific posts:

<!-- File: /app/View/Posts/index.ctp  (edit links added) -->

<h1>Blog posts</h1>
<p><?php echo $this->Html->link("Add Post", array('action' => 'add')); ?></p>
<table>
    <tr>
        <th>Id</th>
        <th>Title</th>
        <th>Action</th>
        <th>Created</th>
    </tr>

<!-- Here's where we loop through our $posts array, printing out post info -->

<?php foreach ($posts as $post): ?>
    <tr>
        <td><?php echo $post['Post']['id']; ?></td>
        <td>
            <?php
                echo $this->Html->link(
                    $post['Post']['title'],
                    array('action' => 'view', $post['Post']['id'])
                );
            ?>
        </td>
        <td>
            <?php
                echo $this->Html->link(
                    'Edit',
                    array('action' => 'edit', $post['Post']['id'])
                );
            ?>
        </td>
        <td>
            <?php echo $post['Post']['created']; ?>
        </td>
    </tr>
<?php endforeach; ?>

</table>

Deleting Posts¶

Next, let’s make a way for users to delete posts. Start with a delete() action in the PostsController:

public function delete($id) {
    if ($this->request->is('get')) {
        throw new MethodNotAllowedException();
    }

    if ($this->Post->delete($id)) {
        $this->Flash->success(
            __('The post with id: %s has been deleted.', h($id))
        );
    } else {
        $this->Flash->error(
            __('The post with id: %s could not be deleted.', h($id))
        );
    }

    return $this->redirect(array('action' => 'index'));
}

This logic deletes the post specified by $id, and uses $this->Flash->success() to show the user a confirmation message after redirecting them on to /posts. If the user attempts to do a delete using a GET request, we throw an Exception. Uncaught exceptions are captured by CakePHP’s exception handler, and a nice error page is displayed. There are many built-in Exceptions that can be used to indicate the various HTTP errors your application might need to generate.

Because we’re just executing some logic and redirecting, this action has no view. You might want to update your index view with links that allow users to delete posts, however:

<!-- File: /app/View/Posts/index.ctp -->

<h1>Blog posts</h1>
<p><?php echo $this->Html->link('Add Post', array('action' => 'add')); ?></p>
<table>
    <tr>
        <th>Id</th>
        <th>Title</th>
        <th>Actions</th>
        <th>Created</th>
    </tr>

<!-- Here's where we loop through our $posts array, printing out post info -->

    <?php foreach ($posts as $post): ?>
    <tr>
        <td><?php echo $post['Post']['id']; ?></td>
        <td>
            <?php
                echo $this->Html->link(
                    $post['Post']['title'],
                    array('action' => 'view', $post['Post']['id'])
                );
            ?>
        </td>
        <td>
            <?php
                echo $this->Form->postLink(
                    'Delete',
                    array('action' => 'delete', $post['Post']['id']),
                    array('confirm' => 'Are you sure?')
                );
            ?>
            <?php
                echo $this->Html->link(
                    'Edit', array('action' => 'edit', $post['Post']['id'])
                );
            ?>
        </td>
        <td>
            <?php echo $post['Post']['created']; ?>
        </td>
    </tr>
    <?php endforeach; ?>

</table>

Using postLink() will create a link that uses JavaScript to do a POST request to delete our post. Allowing content to be deleted using GET requests is dangerous, as web crawlers could accidentally delete all your content.

Routes¶

For some, CakePHP’s default routing works well enough. Developers who are sensitive to user-friendliness and general search engine compatibility will appreciate the way that CakePHP’s URLs map to specific actions. So we’ll just make a quick change to routes in this tutorial.

For more information on advanced routing techniques, see Routes Configuration.

By default, CakePHP responds to a request for the root of your site (e.g., http://www.example.com) using its PagesController, rendering a view called “home”. Instead, we’ll replace this with our PostsController by creating a routing rule.

CakePHP’s routing is found in /app/Config/routes.php. You’ll want to comment out or remove the line that defines the default root route. It looks like this:

Router::connect(
    '/',
    array('controller' => 'pages', 'action' => 'display', 'home')
);

This line connects the URL ‘/’ with the default CakePHP home page. We want it to connect with our own controller, so replace that line with this one:

Router::connect('/', array('controller' => 'posts', 'action' => 'index'));

This should connect users requesting ‘/’ to the index() action of our PostsController.

Conclusion¶

Creating applications this way will win you peace, honor, love, and money beyond even your wildest fantasies. Simple, isn’t it? Keep in mind that this tutorial was very basic. CakePHP has many more features to offer, and is flexible in ways we didn’t wish to cover here for simplicity’s sake. Use the rest of this manual as a guide for building more feature-rich applications.

Now that you’ve created a basic CakePHP application, you’re ready for the real thing. Start your own project and read the rest of the Cookbook and API.

If you need help, there are many ways to get the help you need - please see the Where to Get Help page. Welcome to CakePHP!