Bug report

Calling ctype_alnum with an empty string "" returns always false, we can narrow the param type to at least non-empty-string then in a truthy-scope I'd say.

See https://www.php.net/manual/en/function.ctype-alnum.php

Also https://3v4l.org/oKuT9

Could be done potentially for other ctype_* functions as well most likely.

Code snippet that reproduces the problem

https://phpstan.org/r/4d5dc3e8-e17c-427b-9ff3-f796511d4670

Expected output

Dumped type: non-empty-string

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