PHP create new instance of child class based on existing instance of parent class

Question

I know this is going to be a bit of a weird one, so I'll try to be as brief and as clear as possible.

I am working on a plugin for Grav. I have determined that the most effective way to accomplish my goal is to extend one of the base classes, Pages.

The structure looks something like this:

• index.php creates an instance of grav class.
• Base grav class creates an instance of Pages class and stores it as a service.
• After grav class has finished it's loading process, index.php tells grav to run process on it's service handlers.
• PagesProcessor runs the init() function on the stored Pages class.
• PagesProcessor fires an event signaling that pages have been initalized.
• Plugin receives event.

What this looks like in practical terms.

1. index.php

   $grav = Grav::instance(
       array(
           'loader' => $loader
       )
   );
   

2. Grav.php

   protected static $diMap = [
       .....
       'pages' => 'Grav\Common\Page\Pages',
       'pagesProcessor' => 'Grav\Common\Processors\PagesProcessor',
       .....
   ];
   
   protected $processors = [
       .....
       'pagesProcessor',
       .....
   ];
   
   public static function instance(array $values = [])
   {
       if (!self::$instance) {
           self::$instance = static::load($values);
       .....
       return self::$instance;
   }
   
   protected static function load(array $values)
   {
       $container = new static($values);
       .....
       $container->registerServices($container);
   
       return $container;
   }
   
   protected function registerServices()
   {
       foreach (self::$diMap as $serviceKey => $serviceClass) {
           .....
           $this->registerService($serviceKey, $serviceClass);
           .....
       }
   }
   
   protected function registerService($serviceKey, $serviceClass)
   {
       $this[$serviceKey] = function ($c) use ($serviceClass) {
           return new $serviceClass($c);
       };
   }
   

3. index.php

   try {
       $grav->process();
   } 
   

4. Grav.php

   public function process()
   {
       foreach ($this->processors as $processor) {
           $processor = $this[$processor];
           .....
               $processor->process();
           .....
       }
       .....
   }
   

5. PageProcessor.php

   public function __construct(Grav $container)
   {
       $this->container = $container;
   }
   public function process()
   {
       .....
       $this->container['pages']->init();
       $this->container->fireEvent('onPagesInitialized', new Event(['pages' => $this->container['pages']]));
       .....
   }
   

6. Finally, Plugin.php

   public static function getSubscribedEvents()
   {
       return [
           'onPagesInitialized' => ['onPagesInitialized', 0]
       ];
   }
   
   public function onPagesInitialized(Event $event) {
       // Do things here...
   }
   

Whew... ok.

Now what I would like to do is extend Pages.php (not listed above) so that I can modify some of it's protected properties that don't have setters nativly. The problem is, there is no way to tell grav to use the extended method until AFTER it's been initailized.

I could always create a new instance of my extended class, initailize it, and overwrite the existing instance, but that means effectivly forcing the initailization twice, which means doubling the processing time, and that's super inefficent.

What I would like to do is something like the following:

Pages.php <- I can't change this:

class Pages
{
    protected $grav;

    protected $instances;

    protected $children;

    protected $routes = [];

    public function __construct(Grav $c)
    {
        $this->grav = $c;
    }
    .....
    public function init()
    {
        .....
        $this->instances = [];
        $this->children = [];
        $this->routes = [];

        $this->buildPages();
    }
    .....

PagesExtended.php <- My class

class PagesExtended extends Pages
{
    public function __construct(Pages $original)
    {
        // set the properties of this class to the original instance
        parent = $original;
    }

    public function setInstances(Array $newInstances){
        $this->instances = $newInstances;
    }
    .....
}

Then in my Plugin.php

public function onPagesInitialized(Event $event) {
    // Do things here...
    $this->grav['pages'] = new PagesExtended($event['pages']);
}

The only other thing I can think of is some sort of __call trick.

So.... Thoughts?

EDIT------------------------

Well... I still would like to know if this can be done, but as it turns out grav "freezes" these services so they can't be overridden..... not very happy right now.

Answer 1

It turns out what I was trying to do was impossible in the grav environment, no matter what classes I tried to extend. It could never be done from a plugin because those classes were "frozen" by grav.