根據IP判斷國家

http://bbs.csdn.net/topics/360128267

http://blog.csdn.net/shuangwen163/article/details/8493920

http://hi.baidu.com/dotnet_/item/413356e644d321028d3ea8c7

http://dev.maxmind.com/zh-hans/geoip/geoip2/downloadable/

https://github.com/maxmind/GeoIP2-php

http://www.ip2location.com/buy