将数字转换为EXCEL列名的方法

//递归求解
function R_NumToLetter($num)
{
if($num == 0)
{
return '';
}
$base = 26;
$mod = (int)($num % $base);
$num = (int)($num / $base);
if($mod == 0)
return R_NumToLetter($num - 1).NumToLetter($base);
if($num == 0)
return NumToLetter($mod);
return R_NumToLetter($num).NumToLetter($mod);
}

function NumToLetter($num)
{
if($num == 0)
return '';
$num = (int)$num - 1;
$ord_A = ord('A');
$chr = chr($ord_A + $num);
return $chr;
}