What best practices should be followed to ensure consistent handling of multibyte characters in PHP scripts across different files and functions?

When working with multibyte characters in PHP scripts across different files and functions, it is important to ensure consistent handling to avoid issues such as character encoding errors or unexpected behavior. One best practice is to set the internal encoding to UTF-8 using the `mb_internal_encoding()` function at the beginning of each script or function that deals with multibyte characters.

// Set internal encoding to UTF-8
mb_internal_encoding('UTF-8');