Static methods in PHP

Question

I came to know about static methods called from the instance and can't understand why they can be useful?

EXAMPLE:

class Foo
{
    public static Bar()
    {
    }
}

We can accept method like this:

var $foo = new Foo();
$foo.Bar(); // ??????

Why in PHP you can access static method via the instance of some class but not only via type name?