Problem accessing static objects via self::

Maybe I'm doing something wrong, but I have some code similar to this...

<?php
class a {
function printme() {
return 'hello world';
}
}

class foo {
protected static $blort = null;

function __construct() {
    if (self::$blort == null)
        self::$blort = new a;
}

}

class bar extends foo {
function __construct() {
parent::__construct();
var_dump(self::$blort);
var_dump(self::$blort->printme());
}
}

$b = new bar;
?>

Which gives me:

NULL

Fatal error: Call to a member function printme() on a non-object in
/home/jay/static.php on line 22

Seems that the static property $blort in foo is getting lost somewhere.

Meanwhile, accessing $blort in the parent class via parent::$blort gives a
"Cannot access protected property" error.

Am I doing something wrong here, expecting the wrong behaviour, or is this a
bug?

J