mb_strimwidth() truncates string
str to specified
width. It returns truncated string.
trimmarker is set,
trimmarker is appended to return value.
start is start position offset. Number of
characters from the beginning of string. (First character is 0)
trimmarker is string that is added to the
end of string when string is truncated.
encoding is character encoding. If it is
omitted, internal encoding is used.