The explode() function has a correlating multibyte-safe function in mb_split().
I don't see a correlating function for implode(). Does this imply that implode is already safe for multibyte strings?
As long as your delimiter and the strings in the array contain only well-formed multibyte sequences there should not be any issues.
implode basically is a fancy concatenation operator and I couldn't imagine a scenario where concatenation is not multibyte safe ;)
来源：https://stackoverflow.com/questions/8564967/php-is-the-implode-function-safe-for-multibyte-strings