function detect_mobile_device(){
  
  // check if the user agent value claims to be windows but not windows mobile
  if(stristr($_SERVER['HTTP_USER_AGENT'],'windows')&&!stristr($_SERVER['HTTP_USER_AGENT'],'windows ce')){
    return false;
  }
  // check if the user agent gives away any tell tale signs it's a mobile browser
  if(eregi('up.browser|up.link|windows ce|iemobile|mini|mmp|symbian|midp|wap|phone|pocket|mobile|pda|psp',$_SERVER['HTTP_USER_AGENT'])){
    return true;
  }
  // check the http accept header to see if wap.wml or wap.xhtml support is claimed
  if(stristr($_SERVER['HTTP_ACCEPT'],'text/vnd.wap.wml')||stristr($_SERVER['HTTP_ACCEPT'],'application/vnd.wap.xhtml+xml')){
    return true;
  }
  // check if there are any tell tales signs it's a mobile device from the _server headers
  if(isset($_SERVER['HTTP_X_WAP_PROFILE'])||isset($_SERVER['HTTP_PROFILE'])||isset($_SERVER['X-OperaMini-Features'])||isset($_SERVER['UA-pixels'])){
    return true;
  }
  // build an array with the first four characters from the most common mobile user agents
  $a = array(
                    'acs-'=>'acs-',
                    'alav'=>'alav',
                    'alca'=>'alca',
                    'amoi'=>'amoi',
                    'audi'=>'audi',
                    'aste'=>'aste',
                    'avan'=>'avan',
                    'benq'=>'benq',
                    'bird'=>'bird',
                    'blac'=>'blac',
                    'blaz'=>'blaz',
                    'brew'=>'brew',
                    'cell'=>'cell',
                    'cldc'=>'cldc',
                    'cmd-'=>'cmd-',
                    'dang'=>'dang',
                    'doco'=>'doco',
                    'eric'=>'eric',
                    'hipt'=>'hipt',
                    'inno'=>'inno',
                    'ipaq'=>'ipaq',
                    'java'=>'java',
                    'jigs'=>'jigs',
                    'kddi'=>'kddi',
                    'keji'=>'keji',
                    'leno'=>'leno',
                    'lg-c'=>'lg-c',
                    'lg-d'=>'lg-d',
                    'lg-g'=>'lg-g',
                    'lge-'=>'lge-',
                    'maui'=>'maui',
                    'maxo'=>'maxo',
                    'midp'=>'midp',
                    'mits'=>'mits',
                    'mmef'=>'mmef',
                    'mobi'=>'mobi',
                    'mot-'=>'mot-',
                    'moto'=>'moto',
                    'mwbp'=>'mwbp',
                    'nec-'=>'nec-',
                    'newt'=>'newt',
                    'noki'=>'noki',
                    'opwv'=>'opwv',
                    'palm'=>'palm',
                    'pana'=>'pana',
                    'pant'=>'pant',
                    'pdxg'=>'pdxg',
                    'phil'=>'phil',
                    'play'=>'play',
                    'pluc'=>'pluc',
                    'port'=>'port',
                    'prox'=>'prox',
                    'qtek'=>'qtek',
                    'qwap'=>'qwap',
                    'sage'=>'sage',
                    'sams'=>'sams',
                    'sany'=>'sany',
                    'sch-'=>'sch-',
                    'sec-'=>'sec-',
                    'send'=>'send',
                    'seri'=>'seri',
                    'sgh-'=>'sgh-',
                    'shar'=>'shar',
                    'sie-'=>'sie-',
                    'siem'=>'siem',
                    'smal'=>'smal',
                    'smar'=>'smar',
                    'sony'=>'sony',
                    'sph-'=>'sph-',
                    'symb'=>'symb',
                    't-mo'=>'t-mo',
                    'teli'=>'teli',
                    'tim-'=>'tim-',
                    'tosh'=>'tosh',
                    'treo'=>'treo',
                    'tsm-'=>'tsm-',
                    'upg1'=>'upg1',
                    'upsi'=>'upsi',
                    'vk-v'=>'vk-v',
                    'voda'=>'voda',
                    'wap-'=>'wap-',
                    'wapa'=>'wapa',
                    'wapi'=>'wapi',
                    'wapp'=>'wapp',
                    'wapr'=>'wapr',
                    'webc'=>'webc',
                    'winw'=>'winw',
                    'winw'=>'winw',
                    'xda-'=>'xda-'
                  );
  // check if the first four characters of the current user agent are set as a key in the array
  if(isset($a[substr($_SERVER['HTTP_USER_AGENT'],0,4)])){
    return true;
  }
}

function detect_iphone(){
  if(eregi('iphone',$_SERVER['HTTP_USER_AGENT'])||eregi('ipod',$_SERVER['HTTP_USER_AGENT'])){
    return true;
  }
}

// example 1 - detect and redirect mobile browsers
if(detect_mobile_device()){
  header('Location: mobile/index.html');
  exit;
}

// example 2 - detect and redirect desktop browsers
//if(!detect_mobile_device()){
 // header('Location: http://oreilly.com/');
 // exit;
//}

//function detect_iphone(){
//  if(eregi('iphone',$_SERVER['HTTP_USER_AGENT'])){
//    return true;
//  }
//}

// example 3 - send iphone to specific site
if(detect_iphone()){
 header('Location: mobile/index.html');
 exit;
}

// example 3 - send iphone to specific site
if(!detect_iphone()){
 header('Location: http://news.oreilly.com/index.html');
 exit;
}

?>