Mon. Dec 9th, 2019

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Design Patterns in PHP

2 min read
design patterns php himanshu chittora

design patterns php himanshu chittora

Microsoft design pattern Theory is, “The document introduces patterns and then presents them in a repository, or catalogue, which is organized to help you locate the right combination of patterns that solves your problem”.

There are numerous ways to structure the code and project for your web application, and you can put as much or as little thought as you like into architecting. But it is usually a good idea to follow common patterns because it will make your code easier to manage and easier for others to understand.

Factory

One of the most commonly used design patterns is the factory pattern. In this pattern, a class simply creates the object you want to use. Consider the following example of the factory pattern:

<?php

class Automobile

{

private $vehicleMake;

private $vehicleModel;

 

public function __construct($make, $model)

{

$this->vehicleMake = $make;

$this->vehicleModel = $model;

}

 

public function getMakeAndModel()

{

return $this->vehicleMake . ‘ ‘ . $this->vehicleModel;

}

}

 

class AutomobileFactory

{

public static function create($make, $model)

{

return new Automobile($make, $model);

}

}

 

// have the factory create the Automobile object

$veyron = AutomobileFactory::create(‘Bugatti’, ‘Veyron’);

 

print_r($veyron->getMakeAndModel()); // outputs “Bugatti Veyron”

This code uses a factory to create the Automobile object. There are two possible benefits to building your code this way; the first is that if you need to change, rename, or replace the Automobile class later on you can do so and you will only have to modify the code in the factory, instead of every place in your project that uses the Automobile class. The second possible benefit is that if creating the object is a complicated job you can do all of the work in the factory, instead of repeating it every time you want to create a new instance.

Using the factory pattern isn’t always necessary (or wise). The example code used here is so simple that a factory would simply be adding unneeded complexity. However if you are making a fairly large or complex project you may save yourself a lot of trouble down the road by using factories.

Singleton

A Class has one instance, It provides a global access point to it, Following code will explain about singleton concept.

<?php
   class Singleton {
      public static function getInstance() {
         static $instance = null;
         
         if (null === $instance) {
            $instance = new static();
         }
         return $instance;
      }
      protected function __construct() {
      }
      
      private function __clone() {
      }
      
      private function __wakeup() {
      }
   }
   
   class SingletonChild extends Singleton {
   }
   
   $obj = Singleton::getInstance();
   var_dump($obj === Singleton::getInstance());
   
   $anotherObj = SingletonChild::getInstance();
   var_dump($anotherObj === Singleton::getInstance());
   var_dump($anotherObj === SingletonChild::getInstance()); 
?>

TODO: NEED NEW SINGLETON CODE EXAMPLE

The code above implements the singleton pattern using a static variable and the static creation method getInstance(). Note the following:

  • The constructor __construct() is declared as protected to prevent creating a new instance outside of the class via the new operator.
  • The magic method __clone() is declared as private to prevent cloning of an instance of the class via the clone operator.
  • The magic method __wakeup() is declared as private to prevent unserializing of an instance of the class via the global function unserialize() .
  • A new instance is created via late static binding in the static creation method getInstance() with the keyword static. This allows the subclassing of the class Singleton in the example.

The singleton pattern is useful when we need to make sure we only have a single instance of a class for the entire request lifecycle in a web application. This typically occurs when we have global objects (such as a Configuration class) or a shared resource (such as an event queue).

Strategy

With the strategy pattern you encapsulate specific families of algorithms allowing the client class responsible for instantiating a particular algorithm to have no knowledge of the actual implementation. There are several variations on the strategy pattern, the simplest of which is outlined below:

This first code snippet outlines a family of algorithms; you may want a serialized array, some JSON or maybe just an array of data:

<?php

 

interface OutputInterface

{

public function load();

}

 

class SerializedArrayOutput implements OutputInterface

{

public function load()

{

return serialize($arrayOfData);

}

}

 

class JsonStringOutput implements OutputInterface

{

public function load()

{

return json_encode($arrayOfData);

}

}

 

class ArrayOutput implements OutputInterface

{

public function load()

{

return $arrayOfData;

}

}

By encapsulating the above algorithms you are making it nice and clear in your code that other developers can easily add new output types without affecting the client code.

You will see how each concrete ‘output’ class implements an OutputInterface – this serves two purposes, primarily it provides a simple contract which must be obeyed by any new concrete implementations. Secondly by implementing a common interface you will see in the next section that you can now utilise Type Hinting to ensure that the client which is utilising these behaviours is of the correct type in this case ‘OutputInterface’.

The next snippet of code outlines how a calling client class might use one of these algorithms and even better set the behaviour required at runtime:

<?php

class SomeClient

{

private $output;

 

public function setOutput(OutputInterface $outputType)

{

$this->output = $outputType;

}

 

public function loadOutput()

{

return $this->output->load();

}

}

The calling client class above has a private property which must be set at runtime and be of type ‘OutputInterface’ once this property is set a call to loadOutput() will call the load() method in the concrete class of the output type that has been set.

<?php

$client = new SomeClient();

 

// Want an array?

$client->setOutput(new ArrayOutput());

$data = $client->loadOutput();

 

// Want some JSON?

$client->setOutput(new JsonStringOutput());

$data = $client->loadOutput();

Model-View-Controller

The View acts as GUI, Model Acts as Back End and Control acts as an adapter. Here three parts are interconnected with each other. It will pass the data and access the data between each other.

Deign pattern php

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