PHP如何判断用户是手机浏览还是PC端浏览

<?php
function isMobile(){
	$useragent=isset($_SERVER['HTTP_USER_AGENT']) ? $_SERVER['HTTP_USER_AGENT'] : '';  
		$useragent_commentsblock=preg_match('|\(.*?\)|',$useragent,$matches)>0?$matches[0]:'';        
		function CheckSubstrs($substrs,$text){  
			foreach($substrs as $substr)  
				if(false!==strpos($text,$substr)){  
					return true;  
				}  
				return false;  
		}
		$mobile_os_list=array('Google Wireless Transcoder','Windows CE','WindowsCE','Symbian','Android','armv6l','armv5','Mobile','CentOS','mowser','AvantGo','Opera Mobi','J2ME/MIDP','Smartphone','Go.Web','Palm','iPAQ');
		$mobile_token_list=array('Profile/MIDP','Configuration/CLDC-','160×160','176×220','240×240','240×320','320×240','UP.Browser','UP.Link','SymbianOS','PalmOS','PocketPC','SonyEricsson','Nokia','BlackBerry','Vodafone','BenQ','Novarra-Vision','Iris','NetFront','HTC_','Xda_','SAMSUNG-SGH','Wapaka','DoCoMo','iPhone','iPod');  
	
		$found_mobile=CheckSubstrs($mobile_os_list,$useragent_commentsblock) ||  
				  CheckSubstrs($mobile_token_list,$useragent);  
	
		if ($found_mobile){  
			return true;  
		}else{  
			return false;  
		}  
}
if (isMobile()){
    header('location: ./app/index.php');//如果为手机端，执行跳转
}
else{
    header('location: ./web/index.php');//如果非手机端，执行跳转
}