defining variable as static when it is parameter

[programAngel]

Hi, I have read the following post:
http://net.tutsplus.com/tutorials/ph...injection-huh/
in one of their code, when they call a function they mention when of the given parameter as static.
This is the code:

// Also frequently called "Container"
class IoC {
   /**
    * @var PDO The connection to the database
    */
   protected $db;
 
   /**
    * Create a new instance of Photo and set dependencies.
    */
   public static newPhoto()
   {
      $photo = new Photo;
      $photo->setDB(static::$db);
      // $photo->setConfig();
      // $photo->setResponse();
 
      return $photo;
   }
}
 
$photo = IoC::newPhoto(); 

I am talking about the line:

    $photo->setDB(static::$db); 

what is the meaning of the static in the static::$db ?
I understand what is the meaning of static when you define class, a variable that is common to all the instance of that class.
But when you give it as a parameter, what is the meaning of mention it as static?
And if they do it like the following line:

    $photo->setDB($db); 

what would be the different?

[NogDog]

As I understand it, the static:: keyword means to use the parent's value if/when a child class overrides it (PHP 5.3+):

<?php

class A
{
    static protected $test="class A";
    public function static_test()
    {
        echo static::$test; // Results class b
        echo "<br />\n";
        echo self::$test; // Results class a
    }
}

class B extends A
{
    static protected $test="class B";
}

$obj = new B();
$obj->static_test();
?>