PHP method based on seconds PHP duration

/**
 * 计算持续时长
 *
 * @param int $second 秒数
 * @return string $duration 5天10小时43分钟40秒 
 */
 function second2duration($seconds)
{    
$duration = '';    
$seconds  = (int) $seconds;    
if ($seconds <= 0) {        
return $duration;
    }    
    list($day, $hour, $minute, $second) = explode(&#39; &#39;, gmstrftime(&#39;%j %H %M %S&#39;, $seconds));    
    $day -= 1;    
    if ($day > 0) {        
    $duration .= (int) $day.&#39;天&#39;;
    }    
    if ($hour > 0) {        
    $duration .= (int) $hour.&#39;小时&#39;;
    }    
    if ($minute > 0) {        
    $duration .= (int) $minute.&#39;分钟&#39;;
    }    
    if ($second > 0) {        
    $duration .= (int) $second.&#39;秒&#39;;
    }    
    return $duration;
}