Bilibili AV/BV Video ID Converter

Bilibili.php

<?php

use Exception;

/**
 * Bilibili AV/BV Video ID Converter
 * 
 * @license WTFPL
 */
class Bilibili
{
    /**
     * Convert AVID to BVID
     * 
     * @author mcfx
     * @link https://www.zhihu.com/question/381784377/answer/1099438784
     * @license WTFPL
     * 
     * @param int $avid 
     * @return string 
     */
    public static function av2bv(int $avid): string
    {
        $table = 'fZodR9XQDSUm21yCkr6zBqiveYah8bt4xsWpHnJE7jL5VG3guMTKNPAwcF';

        $tr = [];
        for ($i = 0; $i < 58; $i++) {
            $tr[substr($table, $i, 1)] = $i;
        }

        $s = [11, 10, 3, 8, 4, 6];
        $xor = 177451812;
        $add = 8728348608;

        $avid = ($avid ^ $xor) + $add;
        $r = 'BV1  4 1 7  ';
        $table_arr = str_split($table);
        for ($i = 0; $i < 6; $i++) {
            $r[$s[$i]] = $table_arr[floor($avid / pow(58, $i) % 58)];
        }

        return $r;
    }

    /**
     * Convert BVID to AVID
     * 
     * @author mcfx
     * @link https://www.zhihu.com/question/381784377/answer/1099438784
     * @license WTFPL
     * 
     * @param string $bvid 
     * @return int 
     */
    public static function bv2av(string $bvid): int
    {
        $table = 'fZodR9XQDSUm21yCkr6zBqiveYah8bt4xsWpHnJE7jL5VG3guMTKNPAwcF';

        $tr = [];
        for ($i = 0; $i < 58; $i++) {
            $tr[substr($table, $i, 1)] = $i;
        }

        $s = [11, 10, 3, 8, 4, 6];
        $xor = 177451812;
        $add = 8728348608;

        $r = 0;
        $bvid_arr = str_split($bvid);
        for ($i = 0; $i < 6; $i++) {
            $bvid_arr[$s[$i]];
            if (!isset($bvid_arr[$s[$i]])) {
                throw new Exception('Invalid BVID');
            }
            $r += $tr[$bvid_arr[$s[$i]]] * pow(58, $i);
        }

        $avid = ($r - $add) ^ $xor;

        return $avid;
    }
}