轉換西元日期/民國日期

/*
名稱: 雙向轉換西元日期 - 民國日期
用法: ch_date(來源日期(民國/西元皆可), 來源日期(年月日)分隔符號[選填], 輸出日期(年月日)分隔符號[選填]);
範例: echo ch_date(2006/12/31,'/','-'); // output: 95-12-31
備註: 直接呼叫,將輸出目前民國年份
*/
function ch_date($date="", $from="", $to="") {
  if (!$date) $date = date('Ymd');
  $m = substr($date,-4,2);
  $d = substr($date,-2,2);
  if ($from) {
    if (strlen(@ereg_replace($from,'',$date))>7) {
      $mode = 1;
    } else $mode = 2;
  } else {
    if (strlen($date)>7) {
      $mode = 1;
    } else $mode = 2;
  }
  switch ($mode) {
    case "1":
    if ($from == '') {
      $y = substr($date,0,4)-1911;
    } else {
      $tok = explode($from,$date);
      $y = $tok[0]-1911;
      $m = $tok[1];
      $d = $tok[2];
    }
    break;
    case "2":
    if ($from == '') {
      if (strlen($date)==7) {
        $y = substr($date,0,3)+1911;
      } else $y = substr($date,0,2)+1911;
    } else {
      $tok = explode($from,$date);
      $y = $tok[0]+1911;
      $m = $tok[1];
      $d = $tok[2];
    }
    break;
  }
  $date = $y.$to.$m.$to.$d;
  return $date;
}