php生成excel列名,超过26列大于Z问题解决办法

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 { //开源代码phprm.com 
            $_indexCache[$pColumnIndex] = chr(64 + (($pColumnIndex - 26) / 676)) .  
                                          chr(65 + ((($pColumnIndex - 26) % 676) / 26)) .  
                                          chr(65 + $pColumnIndex % 26);  
        }  
    }  
    return $_indexCache[$pColumnIndex];  
}