自定义的函数如下：

$agent = check_wap();

if( $agent )

{

  header('Location: http://www.jb51.net');

  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; 

  }

}

再来一个从PHP框架剥离的判断是否为手机移动终端的函数：（经过测试，很全面，推荐使用）

function is_mobile_request() 

{ 

 $_SERVER['ALL_HTTP'] = isset($_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 ','acs-','alav','alca','amoi','audi','avan','benq','bird','blac', 

    'blaz','brew','cell','cldc','cmd-','dang','doco','eric','hipt','inno', 

    'ipaq','java','jigs','kddi','keji','leno','lg-c','lg-d','lg-g','lge-', 

    'maui','maxo','midp','mits','mmef','mobi','mot-','moto','mwbp','nec-', 

    'newt','noki','oper','palm','pana','pant','phil','play','port','prox', 

    'qwap','sage','sams','sany','sch-','sec-','send','seri','sgh-','shar', 

    'sie-','siem','smal','smar','sony','sph-','symb','t-mo','teli','tim-', 

    'tosh','tsm-','upg1','upsi','vk-v','voda','wap-','wapa','wapi','wapp', 

    'wapr','webc','winw','winw','xda','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; 

 else

  return false;