Question

can someone explain me the difference between those 2 classes? Why to use satic calls instead of an new object?

class User 
{

  protected $users = array();

/**
 * Create new user
 *
 * @param string $name Username
 * @return array Users
 */
public function create($name)
{
    $this->users[] = $name;
    return $this->users;
}
}

$u = new User();
var_dump($u->create('TEST'));

class User
{
    protected static $users = array();

/**
 * Create new user
 *
 * @param string $name Username
 * @return array Users
 */
public static function create($name)
{
      self::$users[] = $name;
      return self::$users,
}
}

$u = User::create('TEST');
var_dump($u);

Answer 1

Non-static members are bound to a single instance. This is not what is wanted if you want a factory or a registry of instances, so we make the relevant members static instead.