Python and PHP need not be adversaries is my point. Long running, ex. polling, bots, scrapers etc... can be better dealt with in Python as it has dedicated tools and frameworks for those purposes. Backend applications that don't directly deal with the web front allow for better compartmentalisation of priorities and privileges.

Think of it this way; if a layer of your stack has the capability to destroy a system, it's probably best left speaking to another layer that actually speaks to a user.

PHP for web and Python for backend is not a foreign concept and so it makes little sense to apply one hammer to all variety of nails.