fix: string convertion
fix: string convertion

This code comes from Symfony Dumper.
https://github.com/symfony/symfony/blob/b527899f4fb4355fd356eef6f910ea67c5f86192/src/Symfony/Component/VarDumper/Dumper/HtmlDumper.php#L939
I'm not sure this is perfect.

kenjis/CodeIgniter4,kenjis/CodeIgniter4,kenjis/CodeIgniter4,kenjis/CodeIgniter4,kenjis/CodeIgniter4