Inclusionary Zoning is the type of policy you're talking about in parts of the 3rd (and 7th) districts and it's been around in those parts of Philly a few years now. Last year they voted to amend the law and it went into effect this past summer, basically turning what was an optional program that developers wanting to build in the IZ zones (parts of the districts, not the whole district) could just pay into the Housing Trust to avoid. IZ is definitely well-intentioned when it's implemented but may not necessarily help all that much, according to what I've read about it. I did a policy memo project for a class at Temple on the IZ law here in Philly, I've read a few articles about the effects of IZ on affordable housing creation in other cities and the general consensus is that it doesn't usually result in the creation of more affordable units unless the conditions are just right for the developers.

https://better-cities.org/community-growth-housing/inclusionary-zoning-hurts-more-than-helps/
https://www.realclearpolicy.com/articles/2022/02/09/in_philly_theres_no_such_thing_as_free_affordable_housing_815843.html