This function is EXPERIMENTAL. The behaviour of this function, the name of this function, and anything else documented about this function may change without notice in a future release of PHP. Use this function at your own risk.
mb_regex_set_options() sets the default options described by options for multibyte regex functions.
Returns the previous options. If options is omitted, it returns the string that describes the current options.
Note: This function is supported in PHP 4.3.0 or higher.