php如何实现判断是不是手机访问

$agent = check_wap();
 if( $agent )
{
 header('Location: http://www.nowamagic.net');
 exit;
}
// check if wap
function check_wap(){
 // 先检查是否为wap代理，准确度高
 if(stristr($_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; 
 }
}

<?php 
 
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; 
}