Agreed, Python hits a sweet spot, largely because GvR managed to maintain a strong anti-not-invent-here culture in the community.
Also agreed, I'm quite binary, if not caricatural, in my characterization. But it gets the point across, and I trust readers to put grains of salt wherever appropriate.
This being said, if like most projects, yours is more about reusing existing stuff than about writing software components that have never been released by anyone else before, and better-fitting components exist in PHP than in Python, You'll be better off writing ugly and not-fun PHP code. Some people can swallow this, others can't; the latters are probably better off not going the startup way.