php ci框架中header()页面跳转问题

php

使用header函数跳转的时候可以找到指定的url 也能找到页面，但是页面就是不跳转，url不变，这是怎么回事
Request URL:http://localhost/login
Request Method:POST
Status Code:302
Request Headersview source
Accept:*/*
Accept-Encoding:gzip,deflate,sdch
Accept-Language:zh-CN,zh;q=0.8
Connection:keep-alive
Content-Length:67
Content-Type:application/x-www-form-urlencoded
Cookie:PHPSESSID=2k3ap23pdn68ecls5a1kgb8431
Host:localhost
Origin:http://localhost
Referer:http://localhost/
User-Agent:Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.66 Safari/537.36
X-Requested-With:XMLHttpRequest
Form Dataview sourceview URL encoded
username:123
password:e10adc3949ba59abbe56e057f20f883e
role:student
这个是开始的原页面

Request URL:http://localhost/student/index
Request Method:GET
Status Code:200 OK
Request Headersview source
Accept:*/*
Accept-Encoding:gzip,deflate,sdch
Accept-Language:zh-CN,zh;q=0.8
Connection:keep-alive
Cookie:PHPSESSID=2k3ap23pdn68ecls5a1kgb8431
Host:localhost
Referer:http://localhost/
User-Agent:Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.66 Safari/537.36
X-Requested-With:XMLHttpRequest
Response Headersview source
Connection:Keep-Alive
Content-Length:856
Content-Type:text/html
Date:Mon, 18 Nov 2013 14:22:30 GMT
Keep-Alive:timeout=5, max=99
Server:Apache/2.4.4 (Win32) PHP/5.4.16
X-Powered-By:PHP/5.4.16
这个是要跳转到的页面