php excel的列名字：字母和数字互转

来源： \vendor\PHPExcel\PHPExcel\Cell.php

    /**
     *  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 &lt; 26) {
                $_indexCache[$pColumnIndex] = chr(65 + $pColumnIndex);
            } elseif ($pColumnIndex &lt; 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];
    }


    /**
     *  Column index from string
     *
     *  @param  string $pString
     *  @return int Column index (base 1 !!!)
     */
    public static function columnIndexFromString($pString = 'A')
    {
        //  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($_indexCache[$pString]))
            return $_indexCache[$pString];

        //  It's surprising how costly the strtoupper() and ord() calls actually are, so we use a lookup array rather than use ord()
        //      and make it case insensitive to get rid of the strtoupper() as well. Because it's a static, there's no significant
        //      memory overhead either
        static $_columnLookup = array(
            'A' =&gt; 1, 'B' =&gt; 2, 'C' =&gt; 3, 'D' =&gt; 4, 'E' =&gt; 5, 'F' =&gt; 6, 'G' =&gt; 7, 'H' =&gt; 8, 'I' =&gt; 9, 'J' =&gt; 10, 'K' =&gt; 11, 'L' =&gt; 12, 'M' =&gt; 13,
            'N' =&gt; 14, 'O' =&gt; 15, 'P' =&gt; 16, 'Q' =&gt; 17, 'R' =&gt; 18, 'S' =&gt; 19, 'T' =&gt; 20, 'U' =&gt; 21, 'V' =&gt; 22, 'W' =&gt; 23, 'X' =&gt; 24, 'Y' =&gt; 25, 'Z' =&gt; 26,
            'a' =&gt; 1, 'b' =&gt; 2, 'c' =&gt; 3, 'd' =&gt; 4, 'e' =&gt; 5, 'f' =&gt; 6, 'g' =&gt; 7, 'h' =&gt; 8, 'i' =&gt; 9, 'j' =&gt; 10, 'k' =&gt; 11, 'l' =&gt; 12, 'm' =&gt; 13,
            'n' =&gt; 14, 'o' =&gt; 15, 'p' =&gt; 16, 'q' =&gt; 17, 'r' =&gt; 18, 's' =&gt; 19, 't' =&gt; 20, 'u' =&gt; 21, 'v' =&gt; 22, 'w' =&gt; 23, 'x' =&gt; 24, 'y' =&gt; 25, 'z' =&gt; 26
        );

        //  We also use the language construct isset() rather than the more costly strlen() function to match the length of $pString
        //      for improved performance
        if (isset($pString{0})) {
            if (!isset($pString{1})) {
                $_indexCache[$pString] = $_columnLookup[$pString];
                return $_indexCache[$pString];
            } elseif(!isset($pString{2})) {
                $_indexCache[$pString] = $_columnLookup[$pString{0}] * 26 + $_columnLookup[$pString{1}];
                return $_indexCache[$pString];
            } elseif(!isset($pString{3})) {
                $_indexCache[$pString] = $_columnLookup[$pString{0}] * 676 + $_columnLookup[$pString{1}] * 26 + $_columnLookup[$pString{2}];
                return $_indexCache[$pString];
            }
        }
        throw new PHPExcel_Exception("Column string index can not be " . ((isset($pString{0})) ? "longer than 3 characters" : "empty"));
    }