I am aware of fputcsv, but according to this "wontfix" bug fputcsv does not correctly escape input, and its behavior will not be fixed for compatibility reasons. I would prefer an implementation that is compliant with RFC 4180 so Excel and LibreOffice can open it in all cases.
I've tried googling for a library that does this correctly, but there doesn't seem to be a consensus on a decent third party library, instead commonly suggesting the defective fputcsv. I could always roll my own, but I'd prefer not to reinvent the wheel if at all possible.