PHP检测终端设备是平板、手机还是电脑

<?php 

$ua = $_SERVER['HTTP_USER_AGENT'];

function userAgent($ua){

    $iphone = strstr(strtolower($ua), 'mobile'); //Search for 'mobile' in user-agent (iPhone have that)
    $android = strstr(strtolower($ua), 'android'); //Search for 'android' in user-agent
    $windowsPhone = strstr(strtolower($ua), 'phone'); //Search for 'phone' in user-agent (Windows Phone uses that)

    function androidTablet($ua){ //Find out if it is a tablet
        if(strstr(strtolower($ua), 'android') ){//Search for android in user-agent
            if(!strstr(strtolower($ua), 'mobile')){ //If there is no ''mobile' in user-agent (Android have that on their phones, but not tablets)
                return true;
            }
        }
    }
    $androidTablet = androidTablet($ua); //Do androidTablet function
    $ipad = strstr(strtolower($ua), 'ipad'); //Search for iPad in user-agent

    if($androidTablet || $ipad){ //If it's a tablet (iPad / Android)
        return 'tablet';
    }
    elseif($iphone && !$ipad || $android && !$androidTablet || $windowsPhone){ //If it's a phone and NOT a tablet
        return 'mobile';
    }
    else{ //If it's not a mobile device
        return 'desktop';
    }
}

echo userAgent($ua);

/* 判断可以继续跳转到对应的域名 */
//判断如果当前设备不是电脑访问，则跳转到wap;如果当前设备是电脑访问，则跳转到www
if(userAgent($ua) != 'desktop'){

 　　location ='http://wap.baidu.com'+window.location.pathname;
} else {
　　 location ='http://www.baidu.com'+window.location.pathname;

}

?>