<?php
 
print_r(generateExcelColumns(2,30));
function generateExcelColumns($start = 1, $end = 28) {
    if ($start < 1) $start = 1;
    if ($end < $start) $end = $start;
 
    $columns = [];
 
    for ($i = $start; $i <= $end; $i++) {
        $column = '';
        $num = $i;
 
        // 將數字轉成 26 進位字母（類似 base-26，但 Excel 沒有 0，所以 A=1）
        while ($num > 0) {
            $remainder = ($num - 1) % 26;        // 關鍵：減 1 讓餘數從 0~25 對應 A~Z
            $column = chr(65 + $remainder) . $column;
            $num = intval(($num - 1) / 26);      // 繼續處理更高位
        }
 
        $columns[] = $column;
    }
 
    return $columns;
}

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MQoyCjEwCjQyCjExCg==

1
2
10
42
11