function isMobile() {
return preg_match("/(android|avantgo|blackberry|bolt|boost|cricket|docomo|fone|hiptop|mini|mobi|palm|phone|pie|tablet|up.browser|up.link|webos|wos)/i", $_SERVER["HTTP_USER_AGENT"]);
}

if(isMobile()){
// Do something for only mobile users
}
else {
header("location:http://www.dd.dd/hakkimizda.htm");
}