Added Design Patterns page.

pages/Design-Patterns.md

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+---
+layout: page
+title: Design Patterns
+---
+
+# Design Patterns
+
+There are numerous ways to structure the code and project for you 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 to common patterns because it will make
+your code easier to manage and easier for others to understand.
+
+* [Architectural pattern on Wikipedia](https://en.wikipedia.org/wiki/Architectural_pattern)
+* [Software design pattern on Wikipedia](https://en.wikipedia.org/wiki/Software_design_pattern)
+
+## Factory
+
+One of the most commonly used design patterns is the factory pattern. This is a pattern is simply a class that creates
+the object you want to use. Consider the following example of the factory pattern:
+
+{% highlight php %}
+<?php
+class Automobile
+{
+    private $vehicle_make;
+    private $vehicle_model;
+
+    public function __construct($make, $model)
+    {
+        $this->vehicle_make = $make;
+        $this->vehicle_model = $model;
+    }
+
+    public function get_make_and_model()
+    {
+        return $this->vehicle_make . ' ' . $this->vehicle_model;
+    }
+}
+
+class AutomobileFactory
+{
+    public static function create($make, $model)
+    {
+        return new Automobile($make, $model);
+    }
+}
+
+// have the factory create the Automobile object
+$veyron = AutomobileFactory::create('Bugatti', 'Veyron');
+
+print_r($veyron->get_make_and_model()); // outputs "Bugatti Veyron"
+{% endhighlight %}
+
+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.
+
+* [Factory pattern on Wikipedia](https://en.wikipedia.org/wiki/Factory_pattern)
+
+## Front Controller
+
+The front controller pattern is where you have a single entrance point for you web application (e.g. index.php) that
+handles all of the requests. This code is responsible for loading all of the dependencies, processing the request and
+sending the response to the browser. The front controller pattern can be beneficial because it encourages modular code
+and gives you a central place to hook in code that should be run for every request (such as input sanitization).
+
+* [Front Controller pattern on Wikipedia](https://en.wikipedia.org/wiki/Front_Controller_pattern)
+
+## Model-View-Controller
+
+The model-view-controller (MVC) pattern and its relatives HMVC and MVVM let you break up code into logical objects that
+serve very specific purposes. Models serve as a data access layer where data it fetched and returned in formats usable
+throughout your application. Controllers handle the request, process the data returned from models and load views to
+send in the response. And views are display templates (markup, xml, etc) that are sent in the response to the web
+browser.
+
+MVC is the most common architectural pattern used in the popular [PHP frameworks](https://github.com/codeguy/php-the-right-way/wiki/Frameworks).
+
+Learn more about MVC and its relatives:
+
+* [MVC](https://en.wikipedia.org/wiki/Model%E2%80%93View%E2%80%93Controller)
+* [HMVC](https://en.wikipedia.org/wiki/Hierarchical_model%E2%80%93view%E2%80%93controller)
+* [MVVM](https://en.wikipedia.org/wiki/Model_View_ViewModel)