function split4(block $x)
{
	$a = clone $x;
	$a->w /= 2;
	$a->h /= 2;

	$b = clone $a;
	$c = clone $a;
	$d = clone $a;

	$b->x += $b->w;

	$c->y += $c->h;

	$d->x += $d->w;
	$d->y += $d->h;

	return array($a,$b,$c,$d);
}