PHP如何判断浏览器类型

<?php
 2  if(strpos($_SERVER["HTTP_USER_AGENT"],"MSIE 8.0″)) 
 3   echo "Internet Explorer 8.0″; 
 4  else if(strpos($_SERVER["HTTP_USER_AGENT"],"MSIE 7.0″)) 
 5   echo "Internet Explorer 7.0″; 
 6  else if(strpos($_SERVER["HTTP_USER_AGENT"],"MSIE 6.0″)) 
 7   echo "Internet Explorer 6.0″;
 8  else if(strpos($_SERVER["HTTP_USER_AGENT"],"Firefox/3″))
 9   echo "Firefox 3″;
10  else if(strpos($_SERVER["HTTP_USER_AGENT"],"Firefox/2″))
11   echo "Firefox 2″;
12  else if(strpos($_SERVER["HTTP_USER_AGENT"],"Chrome"))
13   echo "Google Chrome";
14  else if(strpos($_SERVER["HTTP_USER_AGENT"],"Safari"))
15   echo "Safari";
16  else if(strpos($_SERVER["HTTP_USER_AGENT"],"Opera"))
17   echo "Opera";
18  else echo $_SERVER["HTTP_USER_AGENT"]; 
19  ?>