Not all is lost. This law may violate the Philadelphia city charter. Just like NYC, Philly has a one subject clause in its charter.
I thought about this too and looked into it before, I really don't think they violated it. Here's the wording from the charter:
§ 2.2-201. Manner of Introduction, Consideration and Passage of Ordinances.
(1) Every proposed ordinance shall be introduced by bill. Every ordinance, except annual budget ordinances and general codifications and revisions of City ordinances, shall contain not more than one subject which shall be clearly and adequately expressed in its title.
It specifically exempts "revisions of City ordinances" from the rule.