You can read the memorial notice from UC Berkeley here.
Phil was a giant in the field of legislation, and his work on statutory interpretation (including his co-authored casebook with Bill Eskridge and Beth Garrett) redefined the field. He was brilliant, insightful, and careful in his scholarship. More than that, he was a wonderful person, generous with his time and modest about his own substantial accomplishments. It is a loss for the field and for all who knew him.