php excel导出列超过26个字母处理

    /**
     *    String from columnindex
     *
     *    @param    int $pColumnIndex Column index (base 0 !!!)
     *    @return    string
     */
    public static function stringFromColumnIndex($pColumnIndex = 0)
    {
        //    Using a lookup cache adds a slight memory overhead, but boosts speed
        //    caching using a static within the method is faster than a class static,
        //        though it's additional memory overhead
        static $_indexCache = array();

        if (!isset($_indexCache[$pColumnIndex])) {
            // Determine column string
            if ($pColumnIndex < 26) {
                $_indexCache[$pColumnIndex] = chr(65 + $pColumnIndex);
            } elseif ($pColumnIndex < 702) {
                $_indexCache[$pColumnIndex] = chr(64 + ($pColumnIndex / 26)) .
                                              chr(65 + $pColumnIndex % 26);
            } else {
                $_indexCache[$pColumnIndex] = chr(64 + (($pColumnIndex - 26) / 676)) .
                                              chr(65 + ((($pColumnIndex - 26) % 676) / 26)) .
                                              chr(65 + $pColumnIndex % 26);
            }
        }
        return $_indexCache[$pColumnIndex];
    }