Description:
------------
Inherit a class with a static method. The static method has static variable in 
it. Now execute both methods and watch the variable. It wont change from one 
class to another.

Test script:
---------------
<?php

class A
{
    function __construct()
    {
        echo get_class($this->getInstance()), PHP_EOL,
		get_class(static::getInstance()), PHP_EOL,
		get_class(self::getInstance()), PHP_EOL;
    }

    public static function getInstance()
    {
        static $getInstance;

        if (null == $getInstance) $getInstance = self::makeInstance();

        return $getInstance;
    }

    public static function makeInstance()
    {
        return new stdClass();
    }
}

$a = new A();

class B extends A
{
    function __construct()
    {
        echo get_class($this->getInstance()), PHP_EOL,
		get_class(static::getInstance()), PHP_EOL,
		get_class(self::getInstance()), PHP_EOL;
    }

    public static function makeInstance()
    {
        return new ArrayObject();
    }
}

$a = new B();

Expected result:
----------------
stdClass
stdClass
stdClass
ArrayObject
ArrayObject
stdClass

Actual result:
--------------
stdClass
stdClass
stdClass
stdClass
stdClass
stdClass