function secondsToString($seconds){
    $bit = array(
        'h' => floor($seconds/3600),
        'm' => floor($seconds/60) % 60,
        's' => $seconds % 60
    );
 
    foreach($bit as $key => $value)
        if ($value > 0) $ret[] = $value . $key;
 
    return join('', $ret);
}