一个用户名，一个密码，一共两个文本框，加上登陆，同在一个表单内，表单可以本页提交，也可以提交到另外写的判断页，判断页需要做的是，获取用户名和密码两个文本框的内容，并读取数据库，与之做对比，用户名和密码匹配成功，则MSG登陆成功，赋值给SESSION，并返回首页。

-A user name, a password, a total of two text box, plus the log in, with a form inside, form can submit this page, also can submit written judgment to another page, judge page need to do is, get your user name and password two