A way to find out the content-type via PHP within page.tpl.php

Hi everybody,

I am loking for a variable or object which tells me what is the
current content-type shown up.
I need this information to build a certain switch within my
page.tpl.php, like:

if($content_type == "page") {
...
}
else if ($content_type == "blogentry") {
...
}

Any ideas?

Thanks alot!

My best,
Soezkan