php判断浏览器类型

<?php
	//baseAgent类，抽象的基类
	abstract class baseAgent
	{
	    abstract function PrintPage();
	}
	//ieAgent类，用于客户端是IE时调用的类
	class ieAgent extends baseAgent
	{
	    function PrintPage()
	    {
	        return "当前浏览器是IE！";
	    }
	}
	//otherAgent类，用于客户端不是IE时调用的类
	class otherAgent extends baseAgent
	{
	    function PrintPage()
	    {
	        return "当前浏览器不是IE！";
	    }
	}
	//判断并创建不同的对象类型，对象名为$currPage
	if(strstr($_SERVER["HTTP_USER_AGENT"], "IEAGENT"))
	{
	    $currPage = new ieAgent();
	} 
	else
	{
	    $currPage = new otherAgent();
	}
	//输出
	echo $currPage->PrintPage();
?>