php如何判断是手机访问还是电脑访问

<?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())  
    echo '手机登录！';  
else
    echo '电脑登录！';  
?>