Parameter types of PHPH 8.0 str_*() functions too strict

[Alexander M. Turek]

Our polyfills of the str_*() functions introduced with PHP 8.0 seem to be a bit too strict about typing. Our version throws a TypeError when null is passed to them while PHP's own implementation treats null like an empty string.

https://3v4l.org/0VShO

This has caused some issues on Symfony after we have migrated to the polyfilled functions, for example symfony/symfony#42290

[Nicolas Grekas]

Indeed! Can you please send a PR? Don't hesitate to merge and release it once it's approved :)

[Alexander M. Turek]

#366