[mg]

Startup times seem to be the same and also negligible:

    time python3 nothing.py
    0.011s

    time php nothing.php
    0.011s

[d-k-bo]

Startup time in Python depends on the program because Python compiles all modules to bytecode before executing them.

[mg]

When I up the loop size by a factor of 10, Python takes 10x longer. So I don't think the compile time plays a role here.

Similar for the PHP version.

    python3 loop.py
    3.450s

    time php loop.php
    0.469s

So PHP is 7x faster for the longer loop.