int转字符串实现方法

<?php


namespace EasySwoole\Utility;


class IntStr
{
    public const intMax = 9223372036854775668;

    private const alphabet = [
        'A','a','B','b','C','c','D','d','E', 'e',
        'F','f','G','g','H','h','I','i','J','j',
        'K','k','L','l','M','m','N','n','O','o',
        'P','p','Q','q','R','r','S','s','T','t',
        'U','u','V','v','W','w','X','x', 'Y','y',
        'Z','z','0','1','2','3','4','5','6','7','8','9'
    ];

    public static function toAlpha($number):string
    {
        if($number < 0 && $number > self::intMax){
            throw new \InvalidArgumentException('number error');
        }
        $alpha = '';
        if($number <= 61){
            return self::alphabet[$number];
        } elseif($number > 61){
            $dividend = ($number + 1);
            while ($dividend > 0){
                $modulo = ($dividend - 1) % 62;
                if($modulo < 0){
                    $modulo = 62+$modulo;
                }
                $alpha = self::alphabet[$modulo] . $alpha;
                $dividend = floor((($dividend - $modulo) / 62));
            }
        }
        return $alpha;
    }

    public static function toNum($string):int
    {
        $alpha_flip = array_flip(self::alphabet);
        $return_value = -1;
        $length = strlen($string);
        for ($i = 0; $i < $length; $i++) {
            $return_value +=
                ($alpha_flip[$string[$i]] + 1) * pow(62, ($length - $i - 1));
        }
        return $return_value;
    }
}

<?php
include "./vendor/autoload.php";
var_dump(\EasySwoole\Utility\IntStr::toNum('JGoSFt2'));
var_dump(\EasySwoole\Utility\IntStr::toAlpha(100000000000000));