ADD php.rst

php session
ADD mediawiki.rst

mediawiki session error and database
Merge branch 'master' of github.com:huiliu/learning.docs.hui
USE bootstrap theme

Need install package dev-python/sphinx-bootstrap-theme
ADD NEW FILE mysql_backup

简述MySQL的备份基础知识
将一些文章加入到主页索引
修复mysql_privileges中的一处语法错误