从Multibyte String Introduction开始：
When you manipulate (trim,split,splice,etc.) strings encoded in a multibyte encoding,you need to use special functions since two or more consecutive bytes may represent a single character in such encoding schemes. Otherwise,if you apply a non-multibyte-aware string function to the string,it probably fails to detect the beginning or ending of the multibyte character and ends up with a corrupted garbage string that most likely loses its original meaning.
