utf8MakeValid
If the provided string is valid UTF-8, return a copy of it. If not, return a copy in which bytes that could not be interpreted as valid Unicode are replaced with the Unicode replacement character (U+FFFD).
For example, this is an appropriate function to use if you have received a string that was incorrectly declared to be UTF-8, and you need a valid UTF-8 version of it that can be logged or displayed to the user, with the assumption that it is close enough to ASCII or UTF-8 to be mostly readable as-is.
Return
a valid UTF-8 string whose content resembles @str
Since
2.52
Parameters
str
string to coerce into UTF-8
len
the maximum length of @str to use, in bytes. If @len < 0, then the string is nul-terminated.