It would appear that Seattle may also send a couple prospects to the Phillies as part of the deal. Speculation is that the players involved would be pitcher Brandon Morrow and/or outfielder Michael Saunders.
Please keep in mind that the details of this deal are unofficial.
We do know that Halladay and his agent are in Philadelphia for a physical and to negotiate a potential extension on his contract with the Phillies. The deal appears to be contingent on the two sides agreeing to a long-term extension.