PHP生成唯一ID方法整理

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1.uniqid()2.session_create_id()3.雪花算法

下面代码摘自互联网<?phpclass SnowFlake{    const TWEPOCH = 1288834974657; // 时间起始标记点,作为基准,一般取系统的最近时间(一旦确定不能变动)    const WORKER_ID_BITS     = 5; // 机器标识位数    const DATACENTER_ID_BITS = 5; // 数据中心标识位数    const SEQUENCE_BITS      = 12; // 毫秒内自增位    private $workerId; // 工作机器ID    private $datacenterId; // 数据中心ID    private $sequence; // 毫秒内序列    private $maxWorkerId     = -1 ^ (-1 << self::WORKER_ID_BITS); // 机器ID最大值    private $maxDatacenterId = -1 ^ (-1 << self::DATACENTER_ID_BITS); // 数据中心ID最大值    private $workerIdShift      = self::SEQUENCE_BITS; // 机器ID偏左移位数    private $datacenterIdShift  = self::SEQUENCE_BITS + self::WORKER_ID_BITS; // 数据中心ID左移位数    private $timestampLeftShift = self::SEQUENCE_BITS + self::WORKER_ID_BITS + self::DATACENTER_ID_BITS; // 时间毫秒左移位数    private $sequenceMask       = -1 ^ (-1 << self::SEQUENCE_BITS); // 生成序列的掩码    private $lastTimestamp = -1; // 上次生产id时间戳    public function __construct($workerId, $datacenterId, $sequence = 0)    {        if ($workerId > $this->maxWorkerId || $workerId < 0) {            throw new Exception('worker Id can't be greater than {$this->maxWorkerId} or less than 0');        }        if ($datacenterId > $this->maxDatacenterId || $datacenterId < 0) {            throw new Exception('datacenter Id can't be greater than {$this->maxDatacenterId} or less than 0');        }        $this->workerId     = $workerId;        $this->datacenterId = $datacenterId;        $this->sequence     = $sequence;    }    public function nextId()    {        $timestamp = $this->timeGen();        if ($timestamp < $this->lastTimestamp) {            $diffTimestamp = bcsub($this->lastTimestamp, $timestamp);            throw new Exception('Clock moved backwards.  Refusing to generate id for {$diffTimestamp} milliseconds');        }        if ($this->lastTimestamp == $timestamp) {            $this->sequence = ($this->sequence + 1) & $this->sequenceMask;            if (0 == $this->sequence) {                $timestamp = $this->tilNextMillis($this->lastTimestamp);            }        } else {            $this->sequence = 0;        }        $this->lastTimestamp = $timestamp;        /*$gmpTimestamp    = gmp_init($this->leftShift(bcsub($timestamp, self::TWEPOCH), $this->timestampLeftShift));        $gmpDatacenterId = gmp_init($this->leftShift($this->datacenterId, $this->datacenterIdShift));        $gmpWorkerId     = gmp_init($this->leftShift($this->workerId, $this->workerIdShift));        $gmpSequence     = gmp_init($this->sequence);        return gmp_strval(gmp_or(gmp_or(gmp_or($gmpTimestamp, $gmpDatacenterId), $gmpWorkerId), $gmpSequence));*/        return (($timestamp - self::TWEPOCH) << $this->timestampLeftShift) |        ($this->datacenterId << $this->datacenterIdShift) |        ($this->workerId << $this->workerIdShift) |        $this->sequence;    }    protected function tilNextMillis($lastTimestamp)    {        $timestamp = $this->timeGen();        while ($timestamp <= $lastTimestamp) {            $timestamp = $this->timeGen();        }        return $timestamp;    }    protected function timeGen()    {        return floor(microtime(true) * 1000);    }    // 左移 <<    protected function leftShift($a, $b)    {        return bcmul($a, bcpow(2, $b));    }}

原文地址:https://blog.51cto.com/phpme/2508142