added flyweight pattern

Structural/Flyweight/CharacterFlyweight.php

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+<?php
+
+namespace DesignPatterns\Structural\Flyweight;
+
+/**
+ * Implements the flyweight interface and adds storage for intrinsic state, if any.
+ * Instances of concrete flyweights are shared by means of a factory.
+ */
+class CharacterFlyweight implements FlyweightInterface {
+
+	/**
+	 * Any state stored by the concrete flyweight must be independent of its context.
+	 * For flyweights representing characters, this is usually the corresponding character code.
+	 * @var string
+	 */
+	private $name;
+
+	/**
+	 * Constructor.
+	 * @param string $name
+	 */
+	public function __construct($name) {
+		$this->name = $name;
+	}
+
+	/**
+	 * Clients supply the context-dependent information that the flyweight needs to draw itself
+	 * For flyweights representing characters, extrinsic state usually contains e.g. the font
+	 * @param string $font
+	 */
+	public function draw($font)
+	{
+		print_r("Character {$this->name} printed $font \n");
+	}
+
+}

Structural/Flyweight/FlyweightFactory.php

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+<?php
+
+namespace DesignPatterns\Structural\Flyweight;
+
+use DesignPatterns\Structural\Flyweight\CharacterFlyweight;
+
+/**
+ * A factory manages shared flyweights. Clients shouldn't instaniate them directly,
+ * but let the factory take care of returning existing objects or creating new ones.
+ */
+class FlyweightFactory {
+	
+	/**
+	 * Associative store for flyweight objects
+     * @var Array
+     */
+	private $pool = array();
+
+	/**
+     * Magic getter
+     * @param string $name
+     * @return Flyweight
+     */
+    public function __get($name)
+    {
+        if (!array_key_exists((string) $name, $this->pool)) {
+            $this->pool[(string) $name] = new CharacterFlyweight((string) $name);
+        }
+        return $this->pool[(string) $name];
+    }
+
+    public function totalNumber()
+    {
+    	return sizeof($this->pool);
+    }
+
+}

Structural/Flyweight/FlyweightInterface.php

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+<?php
+
+namespace DesignPatterns\Structural\Flyweight;
+
+/**
+ * An interface through which flyweights can receive and act on extrinsic state
+ */
+interface FlyweightInterface {
+
+	public function draw($extrinsicState);
+
+}

Structural/Flyweight/Tests/FlyweightTest.php

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+<?php
+
+namespace DesignPatterns\Structural\Flyweight\Tests;
+
+use DesignPatterns\Structural\Flyweight\FlyweightFactory;
+
+/**
+ * FlyweightTest demonstrates how a client would use the flyweight structure
+ * You don't have to change the code of your client
+ */
+class FlyweightTest extends \PHPUnit_Framework_TestCase
+{
+	private $characters = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k',
+		'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z');
+	private $fonts = array('Arial', 'Times New Roman', 'Verdana', 'Helvetica');
+
+	// This is about the number of characters in a book of average length
+	private $numberOfCharacters = 300000;
+
+    public function testFlyweight()
+    {
+        $factory = new FlyweightFactory();
+
+        for ($i = 0; $i < $this->numberOfCharacters; $i++) {
+        	$char = $this->characters[array_rand($this->characters)];
+        	$font = $this->fonts[array_rand($this->fonts)];
+        	$flyweight = $factory->$char;
+        	// External state can be passed in like this:
+        	// $flyweight->draw($font);
+        }
+
+        // Flyweight pattern ensures that instances are shared
+        // instead of having hundreds of thousands of individual objects
+        $this->assertLessThanOrEqual($factory->totalNumber(), sizeof($this->characters));
+    }
+}