用PHP判断是否是手机端

上代码：

/** * 检测是否是手机端 * @return boolean */
function is_mobile(){ 
    $_SERVER['ALL_HTTP'] = isset($_SERVER['ALL_HTTP']) ? $_SERVER['ALL_HTTP'] : '';
    $mobile_browser = '0';
    if(preg_match('/(up.browser|up.link|mmp|symbian|smartphone|midp|wap|phone|iphone|ipad|ipod|android|xoom)/i', strtolower($_SERVER['HTTP_USER_AGENT'])))
        $mobile_browser++;
    if((isset($_SERVER['HTTP_ACCEPT'])) and (strpos(strtolower($_SERVER['HTTP_ACCEPT']),'application/vnd.wap.xhtml+xml') !== false))
        $mobile_browser++;
    if(isset($_SERVER['HTTP_X_WAP_PROFILE']))
        $mobile_browser++;
    if(isset($_SERVER['HTTP_PROFILE']))
        $mobile_browser++;
    $mobile_ua = strtolower(substr($_SERVER['HTTP_USER_AGENT'],0,4));
    $mobile_agents = array(
        'w3c ','','alav','alca','amoi','audi','avan','benq','bird','blac',
        'blaz','brew','cell','cldc','','dang','doco','eric','hipt','inno',
        'ipaq','java','jigs','kddi','keji','leno','lg-c','lg-d','lg-g','',
        'maui','maxo','midp','mits','mmef','mobi','','moto','mwbp','',
        'newt','noki','oper','palm','pana','pant','phil','play','port','prox',
        'qwap','sage','sams','sany','','','send','seri','','shar',
        '','siem','smal','smar','sony','','symb','t-mo','teli','',
        'tosh','','upg1','upsi','vk-v','voda','','wapa','wapi','wapp',
        'wapr','webc','winw','winw','xda',''
    );
    if(in_array($mobile_ua, $mobile_agents)) $mobile_browser++;
    if(strpos(strtolower($_SERVER['ALL_HTTP']), 'operamini') !== false) $mobile_browser++;
    // Pre-final check to reset everything if the user is on Windows
    if(strpos(strtolower($_SERVER['HTTP_USER_AGENT']), 'windows') !== false) $mobile_browser=0;
    // But WP7 is also Windows, with a slightly different characteristic
    if(strpos(strtolower($_SERVER['HTTP_USER_AGENT']), 'windows phone') !== false) $mobile_browser++;
    if($mobile_browser>0) return true;
    return false;
}