PHP实现Snowflake生成分布式唯一ID

<?php

class Snowflake
{
    private $epoch; // 起始时间戳
    private $workerIdBits = 10;
    private $sequenceBits = 12;

    private $maxWorkerId;
    private $maxSequence;

    private $workerIdShift;
    private $timestampLeftShift;
    private $sequenceMask;

    private $lastTimestamp = -1;
    private $sequence = 0;

    public function __construct($workerId, $epoch = 1625097600000)
    {
        $this->maxWorkerId = -1 ^ (-1 << $this->workerIdBits);
        $this->maxSequence = -1 ^ (-1 << $this->sequenceBits);

        $this->workerIdShift = $this->sequenceBits;
        $this->timestampLeftShift = $this->sequenceBits + $this->workerIdBits;
        $this->sequenceMask = -1 ^ (-1 << $this->sequenceBits);

        $this->workerId = $workerId;
        $this->epoch = $epoch;
    }

    public function nextId()
    {
        $timestamp = $this->timeGen();

        if ($timestamp < $this->lastTimestamp) {
            throw new Exception('Clock moved backwards.');
        }

        if ($this->lastTimestamp == $timestamp) {
            $this->sequence = ($this->sequence + 1) & $this->sequenceMask;
            if ($this->sequence == 0) {
                $timestamp = $this->tilNextMillis($this->lastTimestamp);
            }
        } else {
            $this->sequence = 0;
        }

        $this->lastTimestamp = $timestamp;

        return (($timestamp - $this->epoch) << $this->timestampLeftShift) | ($this->workerId << $this->workerIdShift) | $this->sequence;
    }

    protected function timeGen()
    {
        return floor(microtime(true) * 1000);
    }

    protected function tilNextMillis($lastTimestamp)
    {
        $timestamp = $this->timeGen();
        while ($timestamp <= $lastTimestamp) {
            $timestamp = $this->timeGen();
        }
        return $timestamp;
    }
}

// 示例使用
$workerId = 1;
$snowflake = new Snowflake($workerId);
$id = $snowflake->nextId();
echo "生成的ID：{$id}\n";