View Cells
Many applications have small view fragments that can be repeated from page to page, or in different places on the pages. These are often help boxes, navigation controls, ads, login forms, etc. CodeIgniter lets you encapsulate the logic for these presentation blocks within View Cells. They are basically mini-views that can be included in other views. They can have logic built in to handle any cell-specific display logic. They can be used to make your views more readable and maintainable by separating the logic for each cell into its own class.
Simple and Controlled Cells
CodeIgniter supports two types of View Cells: simple and controlled.
Simple View Cells can be generated from any class and method of your choice and does not have to follow any rules, except that it must return a string.
Controlled View Cells must be generated from a class that extends Codeigniter\View\Cells\Cell class which provides additional capability making your View Cells more flexible and faster to use.
Calling a View Cell
No matter which type of View Cell you are using, you can call it from any view by using the view_cell() helper function.
The first parameter is (1) the name of the class and method (Simple Cell) or (2) the name of the class and optional method (Controlled Cell) to call, and the second parameter is an array or string of parameters to pass to the method:
// In a View.
// Simple Cell
<?= view_cell('App\Cells\MyClass::myMethod', ['param1' => 'value1', 'param2' => 'value2']) ?>
// Controlled Cell
<?= view_cell('App\Cells\MyCell', ['param1' => 'value1', 'param2' => 'value2']) ?>
The string that the Cell returns will be inserted into the view where the
view_cell() function was called.
Namespace Omission
New in version 4.3.0.
If you do not include the full namespace for the class, it will assume in can be found in the App\Cells namespace. So, the following example would attempt to find the MyClass class in app/Cells/MyClass.php. If it is not found there, all namespaces will be scanned until it is found, searching within a Cells subdirectory of each namespace:
// In a View.
<?= view_cell('MyClass::myMethod', ['param1' => 'value1', 'param2' => 'value2']) ?>
Passing Parameters as Key/Value String
You can also pass the parameters along as a key/value string:
// In a View.
<?= view_cell('MyClass::myMethod', 'param1=value1, param2=value2') ?>
Simple Cells
Simple Cells are classes that return a string from the chosen method. An example of a simple Alert Message cell might look like this:
<?php
namespace App\Cells;
class AlertMessage
{
public function show(array $params): string
{
return "<div class=\"alert alert-{$params['type']}\">{$params['message']}</div>";
}
}
You would call it from within a view like:
// In a View.
<?= view_cell('AlertMessage::show', ['type' => 'success', 'message' => 'The user has been updated.']) ?>
Additionally, you can use parameter names that match the parameter variables in the method for better readability. When you use it this way, all of the parameters must always be specified in the view cell call:
// In a View.
<?= view_cell('Blog::recentPosts', 'category=codeigniter, limit=5') ?>
<?php
// In a Cell.
namespace App\Cells;
class Blog
{
// ...
public function recentPosts(string $category, int $limit): string
{
$posts = $this->blogModel->where('category', $category)
->orderBy('published_on', 'desc')
->limit($limit)
->get();
return view('recentPosts', ['posts' => $posts]);
}
}
Controlled Cells
New in version 4.3.0.
Controlled cells have two primary goals: (1) to make it as fast as possible to build the cell, and (2) provide additional logic and flexibility to your views, if they need it.
The class must extend CodeIgniter\View\Cells\Cell. They should have a view file
in the same folder. By convention, the class name should be in PascalCase suffixed with Cell and the view should be
the snake_cased version of the class name, without the suffix. For example, if you have a MyCell class, the view file
should be my.php.
Note
Prior to v4.3.5, the generated view file ends with _cell.php. Though v4.3.5 and newer will generate view files
without the _cell suffix, existing view files will still be located and loaded.
Creating a Controlled Cell
At the most basic level, all you need to implement within the class are public properties. These properties will be made available to the view file automatically.
Implementing the AlertMessage from above as a Controlled Cell would look like this:
<?php
// app/Cells/AlertMessageCell.php
namespace App\Cells;
use CodeIgniter\View\Cells\Cell;
class AlertMessageCell extends Cell
{
public $type;
public $message;
}
// app/Cells/alert_message.php
<div class="alert alert-<?= esc($type, 'attr') ?>">
<?= esc($message) ?>
</div>
// Called in main View:
<?= view_cell('AlertMessageCell', 'type=warning, message=Failed.') ?>
Note
If you use typed properties, you must set the initial values:
<?php
// app/Cells/AlertMessageCell.php
namespace App\Cells;
use CodeIgniter\View\Cells\Cell;
class AlertMessageCell extends Cell
{
public string $type = '';
public string $message = '';
}
Generating Cell via Command
You can also create a controlled cell via a built in command from the CLI. The command is php spark make:cell. It takes one argument, the name of the cell to create. The name should be in PascalCase, and the class will be created in the app/Cells directory. The view file will also be created in the app/Cells directory.
php spark make:cell AlertMessageCell
Using a Different View
You can specify a custom view name by setting the view property in the class. The view will be located like any view would be normally:
<?php
namespace App\Cells;
use CodeIgniter\View\Cells\Cell;
class AlertMessageCell extends Cell
{
public $type;
public $message;
protected string $view = 'my/custom/view';
}
Customize the Rendering
If you need more control over the rendering of the HTML, you can implement a render() method. This method allows you to perform additional logic and pass extra data the view, if needed. The render() method must return a string.
To take advantage of the full features of controlled Cells, you should use $this->view() instead of the normal view() helper function:
<?php
namespace App\Cells;
use CodeIgniter\View\Cells\Cell;
class AlertMessageCell extends Cell
{
public $type;
public $message;
public function render(): string
{
return $this->view('my/custom/view', ['extra' => 'data']);
}
}
Computed Properties
If you need to perform additional logic for one or more properties you can use computed properties. These require setting the property to either protected or private and implementing a public method whose name consists of the property name surrounded by get and Property:
// In a View. Initialize the protected properties.
<?= view_cell('AlertMessageCell', ['type' => 'note', 'message' => 'test']) ?>
<?php
// app/Cells/AlertMessageCell.php
namespace App\Cells;
use CodeIgniter\View\Cells\Cell;
class AlertMessageCell extends Cell
{
protected $type;
protected $message;
private $computed;
public function mount(): void
{
$this->computed = sprintf('%s - %s', $this->type, $this->message);
}
public function getComputedProperty(): string
{
return $this->computed;
}
public function getTypeProperty(): string
{
return $this->type;
}
public function getMessageProperty(): string
{
return $this->message;
}
}
// app/Cells/alert_message.php
<div>
<p>type - <?= esc($type) ?></p>
<p>message - <?= esc($message) ?></p>
<p>computed: <?= esc($computed) ?></p>
</div>
Important
You can’t set properties that are declared as private during cell initialization.
Presentation Methods
Sometimes you need to perform additional logic for the view, but you don’t want to pass it as a parameter. You can implement a method that will be called from within the cell’s view itself. This can help the readability of your views:
<?php
// app/Cells/RecentPostsCell.php
namespace App\Cells;
use CodeIgniter\View\Cells\Cell;
class RecentPostsCell extends Cell
{
protected $posts;
public function linkPost($post): string
{
return anchor('posts/' . $post->id, $post->title);
}
}
// app/Cells/recent_posts.php
<ul>
<?php foreach ($posts as $post): ?>
<li><?= $this->linkPost($post) ?></li>
<?php endforeach ?>
</ul>
Performing Setup Logic
If you need to perform additional logic before the view is rendered, you can implement a mount() method. This method will be called just after the class is instantiated, and can be used to set additional properties or perform other logic:
<?php
namespace App\Cells;
use CodeIgniter\View\Cells\Cell;
class RecentPostsCell extends Cell
{
protected $posts;
public function mount(): void
{
$this->posts = model('PostModel')->orderBy('created_at', 'DESC')->findAll(10);
}
}
You can pass additional parameters to the mount() method by passing them as an array to the view_cell() helper function. Any of the parameters sent that match a parameter name of the mount() method will be passed in:
<?php
// app/Cells/RecentPostsCell.php
namespace App\Cells;
use CodeIgniter\View\Cells\Cell;
class RecentPostsCell extends Cell
{
protected $posts;
public function mount(?int $categoryId): void
{
$this->posts = model('PostModel')
->when(
$categoryId,
static fn ($query, $categoryId) => $query->where('category_id', $categoryId)
)
->orderBy('created_at', 'DESC')
->findAll(10);
}
}
// Called in main View:
<?= view_cell('RecentPostsCell', ['categoryId' => 5]) ?>
Cell Caching
You can cache the results of the view cell call by passing the number of seconds to cache the data for as the third parameter. This will use the currently configured cache engine:
// Cache the view for 5 minutes
<?= view_cell('App\Cells\Blog::recentPosts', 'limit=5', 300) ?>
You can provide a custom name to use instead of the auto-generated one if you like, by passing the new name as the fourth parameter:
// Cache the view for 5 minutes
<?= view_cell('App\Cells\Blog::recentPosts', 'limit=5', 300, 'newcacheid') ?>