diff --git a/Mediator/Colleague.php b/Mediator/Colleague.php
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+++ b/Mediator/Colleague.php
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+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Mediator;
+
+/**
+ * Colleague is an abstract colleague who works together but he only knows
+ * the Mediator, not other colleague.
+ */
+abstract class Colleague
+{
+
+    // this ensures no change in subclasses
+    private $mediator;
+
+    // for subclasses
+    protected function getMediator()
+    {
+        return $this->mediator;
+    }
+
+    public function __construct(MediatorInterface $medium)
+    {
+        // in this way, we are sure the concrete colleague knows the mediator
+        $this->mediator = $medium;
+    }
+
+}
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diff --git a/Mediator/Mediator.php b/Mediator/Mediator.php
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+++ b/Mediator/Mediator.php
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+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Mediator;
+
+use DesignPatterns\Mediator\Subsystem;
+
+/**
+ * Mediator is the concrete Mediator for this design pattern.
+ * 
+ * This pattern provides an easy to decouple many components working together.
+ * It is a good alternative over Observer IF you have a "central intelligence",
+ * like a controller (but not in the sense of the MVC).
+ * 
+ * All objects (called Colleague) are coupled only to the MediatorInterface and
+ * it is a good thing because in OOP, one good friend is better than many unreliable.
+ * 
+ * In this example, I have made a "Hello World" with the Mediator Pattern, have fun (^_^)
+ */
+class Mediator implements MediatorInterface
+{
+
+    // you could have an array
+    protected $server;
+    protected $database;
+    protected $client;
+
+    public function setColleague(Subsystem\Database $db, Subsystem\Client $cl, Subsystem\Server $srv)
+    {
+        $this->database = $db;
+        $this->server = $srv;
+        $this->client = $cl;
+    }
+
+    public function makeRequest()
+    {
+        $this->server->process();
+    }
+
+    public function queryDb()
+    {
+        return $this->database->getData();
+    }
+
+    public function sendResponse($content)
+    {
+        $this->client->output($content);
+    }
+
+}
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diff --git a/Mediator/MediatorInterface.php b/Mediator/MediatorInterface.php
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+++ b/Mediator/MediatorInterface.php
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+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Mediator;
+
+/**
+ * MediatorInterface is a contract for the Mediator
+ * This interface is not mandatory but it is better for LSP concerns
+ */
+interface MediatorInterface
+{
+
+    function sendResponse($content);
+
+    function makeRequest();
+
+    function queryDb();
+}
\ No newline at end of file
diff --git a/Mediator/Subsystem/Client.php b/Mediator/Subsystem/Client.php
new file mode 100644
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--- /dev/null
+++ b/Mediator/Subsystem/Client.php
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+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Mediator\Subsystem;
+
+use DesignPatterns\Mediator\Colleague;
+
+/**
+ * Client is a client that make request et get response
+ */
+class Client extends Colleague
+{
+
+    public function request()
+    {
+        $this->getMediator()->makeRequest();
+    }
+
+    public function output($content)
+    {
+        echo $content;
+    }
+
+}
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diff --git a/Mediator/Subsystem/Database.php b/Mediator/Subsystem/Database.php
new file mode 100644
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+++ b/Mediator/Subsystem/Database.php
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+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Mediator\Subsystem;
+
+use DesignPatterns\Mediator\Colleague;
+
+/**
+ * Database is a database service
+ */
+class Database extends Colleague
+{
+
+    public function getData()
+    {
+        return "World";
+    }
+
+}
\ No newline at end of file
diff --git a/Mediator/Subsystem/Server.php b/Mediator/Subsystem/Server.php
new file mode 100644
index 0000000..2f30c57
--- /dev/null
+++ b/Mediator/Subsystem/Server.php
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+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Mediator\Subsystem;
+
+use DesignPatterns\Mediator\Colleague;
+
+/**
+ * Server serves responses
+ */
+class Server extends Colleague
+{
+
+    public function process()
+    {
+        $data = $this->getMediator()->queryDb();
+        $this->getMediator()->sendResponse("Hello $data");
+    }
+
+}
\ No newline at end of file
diff --git a/Tests/Mediator/MediatorTest.php b/Tests/Mediator/MediatorTest.php
new file mode 100644
index 0000000..b673985
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+++ b/Tests/Mediator/MediatorTest.php
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+<?php
+
+/*
+ * DesignPatternPHP
+ */
+
+namespace DesignPatterns\Tests\Mediator;
+
+use DesignPatterns\Mediator\Mediator;
+use DesignPatterns\Mediator\Subsystem\Database;
+use DesignPatterns\Mediator\Subsystem\Client;
+use DesignPatterns\Mediator\Subsystem\Server;
+
+/**
+ * MediatorTest tests hello world
+ */
+class MediatorTest extends \PHPUnit_Framework_TestCase
+{
+
+    protected $client;
+
+    protected function setUp()
+    {
+        $media = new Mediator();
+        $this->client = new Client($media);
+        $media->setColleague(new Database($media), $this->client, new Server($media));
+    }
+
+    public function testOutputHelloWorld()
+    {
+        // testing if Hello World is output :
+        $this->expectOutputString('Hello World');
+        $this->client->request();
+    }
+
+}
\ No newline at end of file