<?php

/* USER-AGENTS
================================================== */
function check_user_agent ( $type = NULL ) {
        $user_agent = strtolower ( $_SERVER[‘HTTP_USER_AGENT’] );
        if ( $type == ‘bot’ ) {
                // matches popular bots
                if ( preg_match ( “/googlebot|adsbot|yahooseeker|yahoobot|msnbot|watchmouse|pingdom.com|
feedfetcher-google/”, $user_agent ) ) {
                        return true;
                        // watchmouse|pingdom.com are “uptime services”
                }
        } else if ( $type == ‘browser’ ) {
                // matches core browser types
                if ( preg_match ( “/mozilla/|opera//”, $user_agent ) ) {
                        return true;
                }
        } else if ( $type == ‘mobile’ ) {
                // matches popular mobile devices that have small screens and/or touch inputs
                // mobile devices have regional trends; some of these will have varying popularity in Europe, Asia, and America
                // detailed demographics are unknown, and South America, the Pacific Islands, and Africa trends might not be represented, here
                if ( preg_match ( “/phone|iphone|itouch|ipod|symbian|android|htc_|htc-|palmos|blackberry|opera mini|iemobile|windows ce|nokia|fennec|hiptop|kindle|mot |mot-|webos/|samsung|sonyericsson|^sie-|nintendo/”, $user_agent ) ) {
                        // these are the most common
                        return true;
                } else if ( preg_match ( “/mobile|pda;|avantgo|eudoraweb|minimo|netfront|brew|teleca|lg;|lge |wap;| wap /”, $user_agent ) ) {
                        // these are less common, and might not be worth checking
                        return true;
                }
        }
        return false;
}

?>

How to use ?

<?php
$ismobile = check_user_agent(‘mobile’);
if($ismobile) {
return ‘yes’;
} else {
return ‘no’;
}
?>