How is Joker still alive in the Post Crisis continuty?

He's so insane that his brain developed a healing factor that mended his brain tissue together and came back completely back to normal.

The good doctors of Gotham tried their best to keep their favorite serial killer to life :)

The writers forgot about it.

Wrong board.

But anyway, the answer is popularity.

It'll save you from death itself.

Just ask Jesus.

WIS

he's so insane death doesn't want him

To be honest , Joker have "die" many times but he still come back. Until now it is a mystery on how he keep coming back

Has anyone here actually read Morrion's full run?

He didn't die in that story. If you continue to read Grant Morrison's run on Batman, he returns and wasn't ever dead in the first place. People have survived getting shot in the skull, it's not impossible.