<?php
/**
 * 將十進制數字轉換為二十六進制字母串
 */
function num2alpha($intNum, $isLower=true)
{
  $num26 = base_convert($intNum, 10, 26);
  $addcode = $isLower ? 49 : 17;
  $result = '';
  for ($i=0; $i<strlen($num26); $i++) {
    $code = ord($num26{$i});
    if ($code < 58) {
      $result .= chr($code+$addcode);
    } else {
      $result .= chr($code+$addcode-39);
    }
  }
  return $result;
}
/**
 * 將二十六進制字母串轉換為十進制數字
 */
function alpha2num($strAlpha)
{
  if (ord($strAlpha{0}) > 90) {
    $startCode = 97;
    $reduceCode = 10;
  } else {
    $startCode = 65;
    $reduceCode = -22;
  }
  $num26 = '';
  for ($i=0; $i<strlen($strAlpha); $i++) {
    $code = ord($strAlpha{$i});
    if ($code < $startCode+10) {
      $num26 .= $code-$startCode;
    } else {
      $num26 .= chr($code-$reduceCode);
    }
  }
  return (int)base_convert($num26, 26, 10);
}