OO php: static and factory classes

[Kirk Cerny]

I have found that this works.

$objName = "Widgit";
$objName->getWidgit();

And this works also.

Widgit::getWidgitStatic();

But this does not.

$objName = "Widgit";
$objName::getWidgitStatic();

Why does the bottom one not work?