1.This document reflects implementation experience with RFC 2109 and obsoletes it.
此文档细化了RFC2109的使用经验，并废弃了相关部份。
2.Defined by the World Wide Web Consortium in RFC 4646, combined with RFC 4647, (obsoletes RFC 3066) for use in HTML and XML documents.
由万维网联盟的RFC4646和RFC4647共同确定，（废除RFC3066），用在HTML和XML文档中。
3.It obsoletes the 5. 1 release and is a recommended upgrade for any PHP V5 users.
它废止了5.1版并被推荐给所有PHPV5用户进行升级。