php - 请解释这个base 62 PHP转换函数/算法

Question

谁能解释一下下面的代码？那或者给我指出一些可以阐明的资源:)

它将整数转换为 base62 字符串。

private static $_characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

private static function _convertBase($num)
{
    $base = strlen(self::$_characters);
    $string = '';

    for ($t = floor(log10($num) / log10($base)); $t >= 0; $t--) {
        $a = floor($num / pow($base, $t));
        $string .= substr(self::$_characters, $a, 1);
        $num = $num - ($a * pow($base, $t));
    }

    return $string;
}

更新:我想问的是:谁能解释一下下面的算法？ :) 谢谢。

Answer 1

你太复杂了:

private static $_characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

private static function _convertBase($num)
{
    $base = strlen(self::$_characters); // 62
    $string = self::$_characters[$num % $base];

    while (($num = intval($num / $base)) > 0)
    {
        $string = self::$_characters[$num % $base] . $string;
    }

    return $string;
}