diff --git a/Command/Command.php b/Command/Command.php
index ea10bb2..8fe9c5b 100644
--- a/Command/Command.php
+++ b/Command/Command.php
@@ -23,7 +23,7 @@ namespace DesignPatterns\Command;
  *   can be implemented with the Command pattern (e.g. vagrant)
  *
  */
-interface Command
+interface CommandInterface
 {
     /**
      * this is the most important method in the Command pattern,
diff --git a/Command/HelloCommand.php b/Command/HelloCommand.php
index 1ba3ecb..baaeda1 100644
--- a/Command/HelloCommand.php
+++ b/Command/HelloCommand.php
@@ -6,25 +6,31 @@ namespace DesignPatterns\Command;
  * This concrete command calls "print" on the Receiver, but an external
  * invoker just know he can call "execute" 
  */
-class HelloCommand implements Command
+class HelloCommand implements CommandInterface
 {
-
+    /**
+     * @var Receiver
+     */
     protected $output;
 
     /**
      * Each concrete command is builded with different receivers.
-     * Can be one, many, none or even other Command in parameters 
+     * Can be one, many, none or even other Command in parameters
+     *
+     * @param Receiver $console
      */
     public function __construct(Receiver $console)
     {
         $this->output = $console;
     }
 
+    /**
+     * execute and output "Hello World"
+     */
     public function execute()
     {
         // sometimes, there is no receiver and this is the command which 
         // does all the work
         $this->output->write('Hello World');
     }
-
-}
\ No newline at end of file
+}
diff --git a/Command/Invoker.php b/Command/Invoker.php
index 75d7a23..f3013e6 100644
--- a/Command/Invoker.php
+++ b/Command/Invoker.php
@@ -12,23 +12,29 @@ namespace DesignPatterns\Command;
  */
 class Invoker
 {
-
+    /**
+     * @var CommandInterface
+     */
     protected $command;
 
     /**
      * In the invoker we find this kind of method for subscribing the command.
      * There can be also a stack, a list, a fixed set...
+     *
+     * @param CommandInterface $cmd
      */
-    public function setCommand(Command $cmd)
+    public function setCommand(CommandInterface $cmd)
     {
         $this->command = $cmd;
     }
 
+    /**
+     * executes the command
+     */
     public function run()
     {
         // here is a key feature of the invoker
         // the invoker is the same whatever is the command
         $this->command->execute();
     }
-
-}
\ No newline at end of file
+}
diff --git a/Command/Receiver.php b/Command/Receiver.php
index a9b6516..6fbed05 100644
--- a/Command/Receiver.php
+++ b/Command/Receiver.php
@@ -11,10 +11,11 @@ namespace DesignPatterns\Command;
  */
 class Receiver
 {
-
+    /**
+     * @param string $str
+     */
     public function write($str)
     {
         echo $str;
     }
-
-}
\ No newline at end of file
+}