[5.x]: StringHelper::replaceMb4 can return null despite being type hinted to string

[xorbdev]

What happened?

Description

If you pass an invalid UTF-8 byte sequence such as "\xC3\x28" to StringHelper::replaceMb4, the preg_replace_callback call will return null and cause an error since the method it is type hinted to string.

Steps to reproduce

1. Call StringHelper::replaceMb4("\xC3\x28", '');

Craft CMS version

5.7.4

PHP version

8.4

Operating system and version

No response

Database type and version

No response

Image driver and version

No response

Installed plugins and versions

[brandonkelly]

Thanks for reporting that! The core issue is that \xC3\x28 is considered invalid UTF-8 data. I’ve fixed this for the next Craft 4 and 5 releases by catching the null response and throwing an InvalidArgumentException instead.

[brandonkelly]

Craft 4.15.3 and 5.7.5 are out with that fix. Thanks again!