此方法根据 ICU 标准执行级别 1 和级别 2 规范化。请参阅 http://userguide.icu-project.org/locale#TOC-Canonicalization.
echo \Locale::canonicalize ( 'en-US.utf8' );
// "en_U"
echo \Locale::canonicalize ( 'FR-fr@EURO' );
// "fr_FR@currency=EUR"
echo \Locale::canonicalize ( '' );
// "en_US_POSIX"