I've been trying to learn CakePhp for a while now but I still can't get alot of stuff. I've been reading a lot and watching videos. I just want to ask a very simple question.
I've been trying to mess with the bookmarks tutorial and i'm watching a video. In the video he baked a component called Validate. In the cmd he typed
bin/cake/bake component Validate
Then a ValidateComponent.php appeared in the component folder in the controller. Now he used the ValidateComponent.php by going to the BookmarksController and adding to the initialize method
$this->loadComponent('Validate');
I just want to ask where did the word validate come from? shouldn't it be ValidateComponent? and where does he get the loadComponent from? I've seen him using $this->method(); or $this->method('string', [array]); I just want to know how the syntax works and what each word means. Sorry for the long explanation. I'm really trying to learn and i'm really confused. thank you very much.
ValidateComponent.php
<?php
namespace App\Controller\Component;
use Cake\Controller\Component;
use Cake\Controller\ComponentRegistry;
/**
* Validate component
*/
class ValidateComponent extends Component
{
/**
* Default configuration.
*
* #var array
*/
protected $_defaultConfig = [];
public function validLimit($limit, $ default)
{
if (is_numeric($limit)){
return $limit;
}
return $default;
}
}
part of BookmarksController.php
public function initialize()
{
parent::initialize();
$this->loadComponent('Validate');
}
I can't seem to find where he got the word 'Validate'
Every controller in your application extends a base Controller Controller or AppController which extends Controller
Controller have bunch of methods, One of these methods is the loadComponent() (See Source)
public function loadComponent($name, array $config = [])
{
list(, $prop) = pluginSplit($name);
$this->{$prop} = $this->components()->load($name, $config);
}
Why Validate instead of ValidateComponent?
Short answer: suffix.
See predefined suffix in App class
CakePHP uses suffix to load classes, When you hit loadComponent() You go to ComponentRegistery class to Register the component, ComponentRegistery will call App class to load class. __loadClass()
Almost everything in CakePHP has a suffix, In your case ValidateComponent has the Component suffix.
return App::className($class, 'Controller/Component', 'Component'); (Source)
I hope this will make more sense to you
$this isn't specifically anything to-do with cake but part of PHP itself. In object oriented context $this refers simply to the current class.
$this->something refers to an object within the current scope. This could be within the current class or from an extends or use.
$this->something(); refers similarly to a method or function within the current scope.
If are using an IDE such as netbeans you can usually click through these references to see the object they refer to so for example if you do in fact use Netbeans you could ctrl-click on $this->loadComponent('Validate'); to see the actual function it refers to.
Regarding where does 'Validate' come from, it's a string you are passing to that object. On the other end it will be used in the function, probably in a switch or if statement to return something.
Eg:
Public function loadComponent($type){
If($type == 'Validation'){
//do something
}
}
Related
I know this has been covered in pieces before, but I am struggling with how to apply it to my code.
I am developing a PHP application in Laravel but want to make my code more modular and testable, which means pulling my logic away from my heavyset controllers and separating them out into separate files and calling them from within the controller.
In one such controller (ImageController), I am calling upon the logic in ImageRepository.php and it looks like this:
<?php
namespace App\Http\Controllers;
use App\Logic\Image\ImageRepository;
use Illuminate\Support\Facades\Input;
class ImageController extends Controller
{
protected $image;
public function __construct(ImageRepository $imageRepository)
{
$this->image = $imageRepository;
}
public function getUpload()
{
return view('pages.upload');
}
public function postUpload()
{
$photo = Input::all();
$response = $this->image->upload($photo);
return $response;
}
/*public function deleteUpload()
{
$filename = Input::get('id');
if(!$filename)
{
return 0;
}
$response = $this->image->delete( $filename );
return $response;
}
*/
}
My problem is I don't understand how this code works, as I got it from another source and want to understand it so I can replicate this architecture elsewhere in my code.
My route when uploading an image is this:
Route::post('upload_image', ['as' => 'upload-post', 'uses' =>'ImageController#postUpload']);
So my first question is, I never call the construct function in my route. It goes right to postUpload(). Does this mean it has no purpose? Also why does the construct function not have a comma between ImageRepository and $imageRepository... from my understanding of the docs you only do that if one of them is a boolean?
Also why does $response = $this->image->upload($photo); mean anything in postUpload()? That function upload() comes from the Repository, is use enough so that it knows what to do? Why does $this->image mean anything, what does the $this refer to? The ImageController class? Is the image in $this->image derived from protected $image?
I guess I should have stuck with regular PHP before moving to the Laravel framework because while I can navigate through Laravel easily enough to make a working application, it seems to be hindering my ability to follow best practices / architecture. AFAIK a controller is mainly something to manipulate data and send it to the view or the database, I don't understand perhaps why it is a class?
Sorry for the multiple questions I am just very confused. I taught myself php on codeacademy but their class declarations and object instances are very easy to follow, this is not. If someone could explain the code to me that would be very helpful.
Thank you!
I never call the construct function in my route. It goes right to postUpload(). Does this mean it has no purpose?
The constructor is automatically called when the controller object is created.
why does the construct function not have a comma between ImageRepository and $imageRepository... from my understanding of the docs you only do that if one of them is a boolean?
ImageRepository is not another argument. It is a type hint (or in PHP 7, a type declaration)
why does $response = $this->image->upload($photo); mean anything in postUpload()? That function upload() comes from the Repository, is use enough so that it knows what to do?
The use is necessary for your controller to be able to use ImageRepository. Once it is loaded into your object in the constructor with $this->image = $imageRepository;, your controller methods have access to its methods, (such as upload) via $this->image.
Why does $this->image mean anything, what does the $this refer to?
Yes, $this does refer to the ImageController class. The PHP manual states:
The pseudo-variable $this is available when a method is called from within an object context. $this is a reference to the calling object
Is the image in $this->image derived from protected $image?
protected $image sets the visibility of the controller object's $image property. It does not assign anything to the property; that is done in the constructor.
You can pass anything to Zend_Registry::set('myWidget', $someWidget), so that it's available later on.
However, when you retrieve it elsewhere, PhpStorm IDE has no clues to the type of 'myWidget'.
<?php
class AwesomeWidget {
public function doBazFlurgle() {
// doesn't matter what exactly happens here
return mt_rand();
}
}
?>
<?php
class FooController {
public function init() {
$someWidget = new AwesomeWidget();
Zend_Registry::set('awesome', $someWidget);
}
public function barAction() {
$this->init();
$awesome = Zend_Registry::get('awesome');
$awesomeNumber = $awesome->doBazFlurgle();
}
}
Navigate to declaration on the ->doBazFlurgle() call gets me a "Cannot find declaration to go to".
I could add a /** #var AwesomeWidget $awesome */ annotation, but that would require editing in many places in a sizable codebase
I could also add a return type annotation to Zend_Registry, but that does not look very maintainable (there are many instances of different classes stored this way).
I could search for the string doBazFlurgle through Find In Path..., but that is not entirely convenient (many keystrokes as opposed to a single Ctrl+click)
I noticed that NetBeans is capable of jumping to the method definition in this exact situation; is there a simple way of doing the same in PHPStorm without going through "search the entire codebase for doBazFlurgle"? I have searched available IDE actions, plugins, and fora; all in vain.
There is a way: as pointed out by #LazyOne, making a list of "what is returned from where" helps the IDE make sense of such code; this is somewhat documented on Jetbrains' website:
<?php
/** #link https://confluence.jetbrains.com/display/PhpStorm/PhpStorm+Advanced+Metadata */
// note that this is not valid PHP code, just a stub for the IDE
namespace PHPSTORM_META {
$STATIC_METHOD_TYPES = [
\Zend_Registry::get('') => [
'awesome' instanceof \AwesomeWidget, // this is the class as seen in the question
'fooSetting' instanceof \Zend_Config, // this came in from application settings
'quuxData' instanceof \ArrayAccess, // an arraylike object
]
];
}
Including this file (named .phpstorm.meta.php by convention) in the project has resolved the issue. This file is not valid PHP - PhpStorm only uses it for typehinting. That way, Zend_Registry::get('awesome')->doBazFlurgle() is correctly resolved as calling the method on an instance of \AwesomeWidget.
There is a workaround:
Position cursor into doBazFlurgle method call (click or cursor movement)
Select word (Ctrl+W)
Navigate to symbol (Ctrl+Alt+Shift+N)
method will be offered in dropdown
Select method (Enter)
Although this is not quite as clumsy as a generic string search, it is still not quite as convenient as the usual navigate to declaration.
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.
$objController = CONTROLLER; <-- I want this to shoo shoo
If I were to just try and use the following, the script file that gets added by aid of the Helper is part of the original Controller array as opposed to the Home controller.
Controller::Add_Script('dominoes'); <-- Will not be part of the Home_Controller array
Question
Please can I have some opinions from the SO community on what you feel the best approach to tackle this would be taking in to account that the controller name will differ? My primary objectives in this exercise are:
Keep the View file VERY simple
Keep the Helper files simple.
Avoid the need to add any code more than necessary to the Home_Controller
I'm currently thinking that one of the best options would be to host the "assets" within a seperate class, just want to know whether it is possible.
Thanks for reading.
First of all, think about your seperation of concerns. Should it really be the responsibility of a controller to manage assets?. Why did you made the method for adding assets static in the first place?
I do not want to use magic methods, globals or have to pass a reference of the controller name to the Helper function.
What are you expecting? If you try to force a class to depend on another class in a completely different scope and context your only option is to use ugly hacks to make your object globally accessible.
Dependency Injection to the rescue
Why should your helper know about what controller and how the controller is treated from the outside?
The only thing your helper should do is to operate with the controller (in your case). It should not try to magically detect what controller is being used. It should just take a controller and operate with it.
class Example_Helper {
public static function Test($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.
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.
Currently I'm using a view-helper to help my debugging process. Basically I call this function and it checks if 1: I'm logged in as a developer by checking a Zend_Session_Namespace variable and 2: if the application is run in debug_mode using Zend_Registry. If both of them are true I show a number of different debug variables and any parameters I give the helper as input.
Originally this function was only intended to check that I got the right info in the objects assigned to the view, but I quickly discovered that it was useful in other places as well. At the moment the function works in controllers using $this->view, and I guess I could technically use something along new Zend_View(); or Zend_Controller_Action_HelperBroker::getStaticHelper('viewRenderer'); to get a view-object in my models, but that is just plain ugly even if it's only for debugging.
So my question is: How can I rebuild this helper into a global function (usable in models, views and Controllers) and still be able to use the Zend_Session_Namespace and Zend_Registry objects, while (as far as possible) maintaining the MVC structure.
I think if you made a static class or a singleton class, you could have all of the desired functionality without breaking your MVC structure at all.
Consider the following simple class with one static function:
<?php
class My_DebugHelper
{
public static function dump()
{
$ns = new Zend_Session_Namespace('the_namespace'); // the namespace you refer to with the developer flag
$debug_mode = Zend_Registry::get('debug_mode');
if (!isset($ns->isDeveloper) || !$ns->isDeveloper || !$debug_mode) {
return;
}
foreach(func_get_args() as $arg) {
Zend_Debug::dump($arg);
}
}
protected function __construct() {}
protected function __clone() {}
}
This code gives you:
The ability to call from anywhere in your application (model, controller, helper, view etc)
All of the protections to prevent it from being executed when called out of context
A simple base that you can expand upon
Depending on your needs, at least one thing you could do is make it static so it could store some of the information rather than access it each call, or add additional methods or specialized parameters so you could pass a Zend_View object to it if necessary and have data injected into the view.
You could call it from anywhere in your application and pass one or more values to dump:
My_DebugHelper::dump($someVar, $this->view, $model->getCustId());
I'm not sure how/what your view helper displays data currently, but hopefully that will help you merge your view helper into the generic class that you can call anywhere.
i just got some more questions while learning PHP, does php implement any built in plugin system?
so the plugin would be able to change the behavior of the core component.
for example something like this works:
include 'core.class.php';
include 'plugin1.class.php';
include 'plugin2.class.php';
new plugin2;
where
core.class.php contains
class core {
public function coremethod1(){
echo 'coremethod1';
}
public function coremethod2(){
echo 'coremethod2';
}
}
plugin1.class.php contains
class plugin1 extends core {
public function coremethod1(){
echo 'plugin1method1';
}
}
plugin2.class.php contains
class plugin2 extends plugin1 {
public function coremethod2(){
echo 'plugin2method2';
}
}
This would be ideal, if not for the problem that now the plugins are dependable on each other, and removing one of the plugins:
include 'core.class.php';
//include 'plugin1.class.php';
include 'plugin2.class.php';
new plugin2;
breaks the whole thing...
are there any proper methods to doing this?
if there are not, them i might consider moving to a different langauge that supports this...
thanks for any help.
edit:
obviously it is my understanding that is lacking, so here is a
attempt at a clarification.
core.class.php contains anything...
plugin1.class.php contains anything...
plugin2.class.php contains anything...
include 'core.class.php';
include 'plugin1.class.php';
include 'plugin2.class.php';
$core = new core;
$core->coremethod1();//outputs plugin2method1
whereas:
include 'core.class.php';
include 'plugin2.class.php';
$core = new core;
$core->coremethod1();//outputs plugin1method1
I'm interested in any implementation, even one not involving classes
for example
include 'core.php';
//does core stuff
include 'core.php';
include 'plugin1';
//does extended core stuff
include 'core.php';
include 'plugin2';
//does extended core stuff
include 'core.php';
include 'plugin2';
include 'plugin1';
//does very extended core stuff
including a file needs to change the application behavior. for it to have any meaning.
I do not know what this is called either, so point me at the proper naming if there is any.
You are misusing the term "plugin". A plugin is generally a package of code that extends or alters the base functionality of a system - to make actual PHP plugins (which in the PHP world are called extensions) you'd be writing C or C++.
What you're describing here is merely including classes or class trees into the current execution for usage. And there is a way to bring them into the current execution context 'automatically', and that's via the autoload system.
If, after you've read the documentation on autoloading, you are still unsure of how to move forward, comment here and I will help you along.
EDIT
Ok, I see what you're after. You can't do exactly what you're after. When you execute new core; an instance of the class core will be returned - you can't modify that at all.
However, if you are willing to modify how you create instances of core, then I think I have something that could work for you, and it might look something like this.
class core {
public function coremethod1(){
echo 'coremethod1';
}
public function coremethod2(){
echo 'coremethod2';
}
/**
* #return core
*/
final public static function create()
{
// listed in order of preference
$plugins = array( 'plugin2', 'plugin1' );
foreach ( $plugins as $plugin )
{
if ( class_exists( $plugin ) )
{
return new $plugin();
}
}
return new self;
}
}
class plugin1 extends core {
public function coremethod1(){
echo 'plugin1method1';
}
}
class plugin2 extends plugin1 {
public function coremethod2(){
echo 'plugin2method2';
}
}
$core = core::create();
// test what we have
echo get_class( $core ), '<br>'
, $core->coremethod1(), '<br>'
, $core->coremethod2()
;
If your only concern is that not including plugin1 will create an error, then you can resort to autoloading to have plugin2 load plugin1 automatically:
From the comments in the PHP Manual on spl_autoload
// Your custom class dir
define('CLASS_DIR', 'class/')
// Add your class dir to include path
set_include_path(get_include_path().PATH_SEPARATOR.CLASS_DIR);
// You can use this trick to make autoloader look
// for commonly used "My.class.php" type filenames
spl_autoload_extensions('.class.php');
// Use default autoload implementation
spl_autoload_register();
If, however, you are looking for a traits/mixin-like feature, then the answer is no. PHP does not support this as of now. At least not without patching the core or resorting to these two APIs you do not want to use in production code.
The proper way to change how an object behaves at runtime would be to use Decorators:
$class = new BasicCache( new BasicValidators ( new Basic ) );
or Strategy patterns:
$class = new Basic;
$class->setStrategy(function() { return 'foo'} );
echo $class->callStrategy(); // foo
$class->setStrategy(function() { return 'bar'} );
echo $class->callStrategy(); // bar
See http://sourcemaking.com/design_patterns for the most common patterns.
EDIT Here is an example of how to create plugins with decorators. Assume, we have a game of some sort where some non-player characters walk around in a virtual space and greet the main character from time to time. That's all they do right now. We want some variation on how they greet though, which is why we need our plugins/decorators in this scenario.
First we create an interface that defines some methods any object able to greet should have. We don't care about what it does when these methods are invoked on a specific object. We just want to make sure that the methods are available and that they are called with a clearly defined input:
interface GreetInterface
{
public function greet($name);
public function setGreeting($greeting);
}
An interface is basically a contract any implementing object must fulfill. In our case, the contract says, if you are an object that can greet, you have to have two methods. Implement them any way you like, but have these methods.
Let's build our non-player character classes now, implementing this interface
class Dude implements GreetInterface
{
protected $greeting = 'hello';
public function greet($name)
{
return sprintf('%s %s', $this->greeting, $name);
}
public function setGreeting($greeting)
{
$this->greeting = $greeting;
return $this;
}
}
That's pretty straigtforward I guess. The Dude class just defines the two methods from the interface. When greet() is called, it will fetch the string stored in greeting and prepend to the param passed to the greet method. The setGreeting method allows us to change the greeting at runtime. Note: you could add a getter as well (I was just lazy)
Now on to the plugins. We will create an abstract GreetPlugin class to contain some shared boilerplate code, simply because we don't want to duplicate code in our actual plugins. The abstract plugin class will implement the GreetInterface, so we can make sure all subclasses implement the interface too.
Since Dude already implements the interface as well, we could have the plugins extend Dude, but that would be conceptually wrong, because extending creates an is-a relationship, but a plugin is not a Dude.
abstract class GreetPluginAbstract implements GreetInterface
{
protected $inner;
public function __construct(GreetInterface $inner)
{
$this->inner = $inner;
}
public function setGreeting($greeting)
{
$this->inner->setGreeting($greeting);
return $this;
}
public function greet($name)
{
return $this->inner->greet($name);
}
}
The plugin class accepts one argument when initialized: any class implementing the GreetInterface. The TypeHint makes sure, the class fulfills the contract. That's required, because, as you can see in the code, our plugins will need to call the methods in the interface on the class passed through the constructor. If we had extended from Dude, we would now be able to wrap dudes into dudes, which is a bit odd. Another reason for not doing it.
Now on to the first plugin. We want some of our dudes to speak with a fancy french accent, which means they use âccénts all over the place, but cannot pronounce a proper h. Disclaimer: yes, I know that's a cliche. Please bear with my examples
class FrenchPlugin extends GreetPluginAbstract
{
public function greet($name) {
return str_replace(array('h', 'e'), array('', 'é'),
$this->inner->greet($name));
}
}
Since the Plugin extends the abstract plugin, we can now focus on the actual code that modifies how a regular dude would do his greeting. When greet() is called, we call greet() on the wrapped element and then remove all h characters and turn all es into és. Everything else is unmodified abstract behavior.
In another plugin, we want to change the wording of the greeting, so we have some dudes say Heya, instead of just Hello. Just to add some variation.
class EasyGoingPlugin extends GreetPluginAbstract
{
protected $inner;
public function __construct(GreetInterface $inner) {
$this->inner = $inner->setGreeting('heya');
parent::__construct($inner);
}
}
This way we only override the constructor, because the greet method should just return whatever it will be. So we call the setGreeting method on the object passed to this plugin. Because the object has to implement the GreetInterface, we can be sure this works.
Note that I am assigning the return value of setGreeting as the inner object. This is possible because I return $this, whenever setMethod is called. This cannot be enforced through the interface, so you cannot rely on this form the interface. I just added it to show another technique: method chaining.
With two plugins done, we feel we have enough variation. Now we only need a convenient way to create Dudes. For that we create a small class like this:
class DudeBuilder
{
public static function build()
{
$dude = new Dude();
$decorators = func_get_args();
foreach($decorators as $decorator) {
$decorator .= "Plugin";
// require_once $decorator;
$dude = new $decorator($dude);
}
return $dude;
}
}
Note: I always mix up Builder and AbstractFactory, so if the above is a Factory, well, then it's a factory. Check out the design patterns links I gave earlier on ;)
All this Builder does, is create a regular dude and then wrap/decorate it into/with whatever plugins we tell it to use and than return it. Because the builder encapsulates no own state, we make the build method static.
For this example I assume you used the autoloading code I gave right on top. If not, you can include the plugin files in the foreach loop. Lazy loading them only when they are needed will give you a few microseconds faster load times over including them all on top. Hopefully, this also explains what I meant in the various comments when I argued the behavior should not be controlled by a file inclusion. The file inclusion is just a necessity. You cannot use a class that is not know to PHP. But that the class is actually used, is controlled by our code alone, by passing in the plugin names to the build method.
Let's do this now
$regularDude = DudeBuilder::build();
$frenchDude = DudeBuilder::build('French');
$easygoingDude = DudeBuilder::build('EasyGoing');
$frenchEasyGoingDude = DudeBuilder::build('French', 'EasyGoing');
This is effectively the same as doing:
$regularDude = new Dude;
$frenchDude = new FrenchPlugin(new Dude);
$easygoingDude = new EasyGoingPlugin(new Dude);
$frenchEasyGoingDude = new FrenchPlugin(new EasyGoingPlugin(new Dude));
With just two plugins, we can now create three types of Dudes. Let's have them greet you:
echo $regularDude->greet('Yuri'), PHP_EOL,
$frenchDude->greet('Yuri'), PHP_EOL,
$easygoingDude->greet('Yuri'), PHP_EOL,
$frenchEasyGoingDude->greet('Yuri'), PHP_EOL;
// gives
hello Yuri
éllo Yuri
heya Yuri
éya Yuri
We can now create additional plugins to decorate our basic classes with. If for some reason, you decide your game should have talking horses or cars as well, you could also create a class Car or Horse and have it implement the greet interface too and add a Builder for them. You can then reuse the plugins to create French EasyGoing Cars or Horses.
PHP core can be extended with PECL extensions (which are C++, I believe).
Core functions can be overridden (if you have the APD PECL extension installed) with override_function
User functions can be executed with call_user_func.
Maybe if you could explain what you are planning, we'd be able to offer a better answer?
Your code is breaking because plugin2 extends plugin1, and you're not including the plugin1 class. Why not make class plugin2 extend core? That seems to be what you're going for.