PHP 判断用户是否手机访问

$agent = check_wap();
if( $agent )
{
    header('Location: http://www.lewanau.com');
    exit;
}

// check if wap
function check_wap(){
    // 先检查是否为wap代理，准确度高
    if(stristr($_SERVER['HTTP_VIA'],"wap")){
        return true;
    }
    // 检查浏览器是否接受 WML.
    elseif(strpos(strtoupper($_SERVER['HTTP_ACCEPT']),"VND.WAP.WML") > 0){
        return true;
   }
   //检查USER_AGENT
   elseif(preg_match('/(blackberry|configuration\/cldc|hp |hp-|htc |htc_|htc-|iemobile|kindle|midp|mmp|motorola|mobile|nokia|opera mini|opera |Googlebot-Mobile|YahooSeeker\/M1A1-R2D2|android|iphone|ipod|mobi|palm|palmos|pocket|portalmmm|ppc;|smartphone|sonyericsson|sqh|spv|symbian|treo|up.browser|up.link|vodafone|windows ce|xda |xda_)/i', $_SERVER['HTTP_USER_AGENT'])){
        return true;
    }
    else{
        return false;
   }
}