php - Base10到base64网址缩短

我正在为正在学习php的项目编写url缩短功能，这是代码(顺便说一句，我想这里global并不是一件好事:P):

$alphabet = array(1 => "a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z",
                "A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z",
                "0","1","2","3","4","5","6","7","8","9","_","-");

function shorten($id){
    global $alphabet;
    $shortenedId = "";
    while($id>0){
        $remainder = $id % 64;
        $id = $id / 64;
        $shortenedId = $alphabet[$remainder].$shortenedId;
    }
    return $shortenedId;
}

该代码取自this Wikipedia article并适用于php。我的问题是，当我将64的倍数传递给函数时，我得到了一个错误的结果(出于我的目的)，例如128返回不正确的b，应该是aaa，但是对于3位数字来说太长了数字。

我也开始认为这段代码有问题，如果我将1'000'000'000'000作为$id传递，我得到nItOq ...我觉得这是错误的，因为诸如bit.ly这样的网址缩短服务返回了如果我使用6个数字ID，我认为该算法并不比他们的算法更好。

因此，有两个问题:

您在上面的代码中发现任何错误了吗？

如何管理64多个ID？我是否必须忽略它们并传递给下一个？

最佳答案

仅需进行一些小调整，主要的两个调整是使字母零索引而不是一索引，并在除法之前从id中减去余数

function shorten($id)
{
    $alphabet = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_-';
    $shortenedId = '';
    while($id>0) {
        $remainder = $id % 64;
        $id = ($id-$remainder) / 64;
        $shortenedId = $alphabet{$remainder} . $shortenedId;
    };
    return $shortenedId;
}

这是进一步的修改版本...嗯，我就像

function shorten($id, $alphabet='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-')
{
    $base = strlen($alphabet);
    $short = '';
    while($id) {
        $id = ($id-($r=$id%$base))/$base;
        $short = $alphabet{$r} . $short;
    };
    return $short;
}

编辑:对串联进行排序，使其与OP相同

关于php - Base10到base64网址缩短，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/3199771/