<?php

class logs
{

  static $_last_check = array();

  static function rotate($filepath)
  {
    $limit = (1024 * 1024 * 20);

    $date_obj = new DateTime('-3 min');
    $check_time = $date_obj->format('U');

    if (!isset(self::$_last_check[$filepath]) || self::$_last_check[$filepath] < $check_time)
    {
      clearstatcache();

      if (file_exists($filepath) && filesize($filepath) > $limit)
      {
        $n = 1;
        while (file_exists($filepath . '.' . $n))
          $n++;
        if (copy($filepath, $filepath . '.' . $n))
        {
          $handle = fopen($filepath, 'r+');
          ftruncate($handle, 0);
          fclose($handle);
        }
      }

      self::$_last_check[$filepath] = $check_time;
    }

    return;
  }

}