PHP late static bound referencing

Question

Situation

In this web app I am building there is a "bootstrap" sequence that defines (through constants) and initiates an extended controller. Currently, the controller keeps track of assets (script files, css, etc.) that will be deployed at the later render stage through a series of static variables. I will simplify the code here, think of it as pseudo-PHP.

/* CONTROLLER CLASS */
class Controller {
    protected static $aryScriptFiles = array();
    public function __construct() {
        /* Behaviour */
        /* Some logic that identifies/calls Home_Controller method Index */
    }
    public static function Add_Script($strFileName) {
        static::$aryScriptFiles[] = $strFileName;
    }    
}

/* HOME_CONTROLLER CLASS */
class Home_Controller extends Controller {
    protected static $aryScriptFiles = array('default', 'carousel', 'etc');
    protected function Index() {
        /* Behaviour */
        /* Load the view as an include. It is "part" of the User_Controller */ 
    }
}

/* EXAMPLE_HELPER */
class Example_Helper {
    public static function Test() {

         /* THE NEXT LINE IS IMPORTANT FOR THE QUESTION */
         $objController = CONTROLLER;
         $objController::Add_Script('dominoes');
    }    
}

/* INDEX VIEW FILE */
<h1>Welcome!</h1>
<?php
echo get_class(); <-- Would echo 'User_Controller'
Example_Helper::Test();

/* Simplification of render process */
foreach(static::$aryScriptFiles as $strFileName) {
    /* Render the HTML script tag */
}
?>

Flow

Ok, given the above there is a bootstrap that ends up calling User_Controller. For examples sake, I have simply defined them to let you know what state the script will follow.

$strControllerName = 'User_Controller';
define('CONTROLLER', $strControllerName);
$objController = new $strControllerName();

What you end up with is the aryScriptFiles array having 4 entries and this works great.

Problem

Before reading on, please note I do not want to use magic methods, globals or have to pass a reference of the controller name to the Helper function.

I would like to try and remove the line in the helper file that pulls the current controller name to a variable from the constant.

$objController = CONTROLLER; <-- I want this to shoo shoo

If I were to just try and use the following, the script file that gets added by aid of the Helper is part of the original Controller array as opposed to the Home controller.

Controller::Add_Script('dominoes'); <-- Will not be part of the Home_Controller array

Question

Please can I have some opinions from the SO community on what you feel the best approach to tackle this would be taking in to account that the controller name will differ? My primary objectives in this exercise are:

• Keep the View file VERY simple
• Keep the Helper files simple.
• Avoid the need to add any code more than necessary to the Home_Controller

I'm currently thinking that one of the best options would be to host the "assets" within a seperate class, just want to know whether it is possible.

Thanks for reading.

Answer 1

First of all, think about your seperation of concerns. Should it really be the responsibility of a controller to manage assets?. Why did you made the method for adding assets static in the first place?

I do not want to use magic methods, globals or have to pass a reference of the controller name to the Helper function.

What are you expecting? If you try to force a class to depend on another class in a completely different scope and context your only option is to use ugly hacks to make your object globally accessible.

Dependency Injection to the rescue

Why should your helper know about what controller and how the controller is treated from the outside?

The only thing your helper should do is to operate with the controller (in your case). It should not try to magically detect what controller is being used. It should just take a controller and operate with it.

class Example_Helper {
    public static function Test($controller) {
         $controller::Add_Script('dominoes');
    }    
}

Example_Helper::Test($objController);

Since the addScript() method and the $aryScriptFiles property is static anyways, you could also just call the method in the helper on the parent controller. It would make no difference.

Also why do you want to talk to your controller from the view? The view should be "dumb" it should not be able to hold and operate with data except those that were passed to it by the controller.

Wouldn't it make more sense to add functionality to your controller or one of it's services that passes the required assets to your view, instead of forcing the view to get it's data from from the controller by itself?

I think there are a few logical flaws in your code here. Especially your usage of static properties and methods. If you could clarify that a bit I could go in detail a bit.

Answer 2

Apart from architectural concerns (assets should indeed be managed by a separate AssetManager) your problem can be relatively easily solved because of PHP's rather peculiar own architecture, specifically exposed through methods like get_called_class. This allows you to write code like this:

$assets = [];  // Global for brevity of example

class Base {
  static function addScript($script)
  {
    global $assets;

    $myName = get_called_class();
    $assets[$myName][] = $script;
  }
}

class Derived extends Base {
  public function __construct()
  {
    self::addScript('test');
  }
}

$foo = new Derived();
var_dump($assets);

Which will then output the following:

array(1) {
  ["Derived"]=>
  array(1) {
    [0]=>
    string(4) "test"
  }
}

Note that using get_class instead of get_called_class would here show the array's name as Base instead of Derived, while Derived is what you need. This way you can embed helper functions in Controller, which automatically derive the class name and forward it to the central asset manager.