2011-06-01
If damage dealt to Phyrexian Hydra can't be prevented (due to Leyline of Punishment, for example), it will be dealt as normal and won't cause Phyrexian Hydra to put -1/-1 counters on itself.
2011-06-01
If multiple damage prevention effects, including Phyrexian Hydra's, are attempting to prevent damage that would be dealt to Phyrexian Hydra, its controller chooses which to apply.