Symfony version(s) affected

allk

Description

Woooo, I faced a very hard to find bug!
I use bopoda/robots-txt-parser, and they hardcoded something very strange in a class:

// Strip invalid characters from UTF-8 strings
ini_set('mbstring.substitute_character', "none");

I already open an issue there to fix the issue.

But I think we can protect Symfony for such issue.

How to reproduce

I created a small reproducer.
(Un)Comment the following line, and run the script

new RobotsTxtParser('');

You'll see the output is different.

Possible Solution

Force the following line in our code

ini_set('mbstring.substitute_character', "");

Additional Context

I'm not sure we have to do this. But let's discuss it!