Snowflake algo sample (PHP)

Snowflake.php

<?php

use Exception;

/**
 * Class Snowflake
 *
 * @see https://github.com/twitter/snowflake
 */
class Snowflake
{
    /**
     *
     */
    const SIGN_BIT = 1;
    /**
     *
     */
    const TIMESTAMP_BIT = 41;
    /**
     *
     */
    const DATACENTER_BIT = 5;
    /**
     *
     */
    const MACHINE_BIT = 5;
    /**
     *
     */
    const SEQUENCE_BIT = 12;
    /**
     *
     */
    const MAX_TIMESTAMP_DEC = (1 << self::TIMESTAMP_BIT) - 1;
    /**
     *
     */
    const MAX_DATACENTER_DEC = (1 << self::DATACENTER_BIT) - 1;
    /**
     *
     */
    const MAX_MACHINE_DEC = (1 << self::MACHINE_BIT) - 1;
    /**
     *
     */
    const MAX_SEQUENCE_DEC = (1 << self::SEQUENCE_BIT) - 1;
    /**
     *
     */
    const TIMESTAMP_OFFSET = self::DATACENTER_BIT + self::MACHINE_BIT + self::SEQUENCE_BIT;
    /**
     *
     */
    const DATACENTER_OFFSET = self::MACHINE_BIT + self::SEQUENCE_BIT;
    /**
     *
     */
    const MACHINE_OFFSET = self::SEQUENCE_BIT;
    /**
     *
     */
    const EPOCH_TIME = 1514260211335; // 2017-12-26 11:50
    /**
     * @var int
     */
    protected $datacenterId;
    /**
     * @var int
     */
    protected $machineId;
    /**
     * @var
     */
    private $_lastTimestamp;
    /**
     * @var int
     */
    private $_sequence = 0;

    /**
     * Snowflake constructor.
     * @param int $datacenterId
     * @param int $machineId
     * @throws \Exception
     */
    public function __construct($datacenterId = 0, $machineId = 0)
    {
        $this->datacenterId = $datacenterId;
        $this->machineId = $machineId;

        $this->validate();
    }

    /**
     * Simple validation.
     *
     * @throws \Exception
     */
    protected function validate()
    {
        if ($this->datacenterId > self::MAX_DATACENTER_DEC || $this->datacenterId < 0) {
            throw new Exception('Illegal datacenter id.');
        }

        if ($this->machineId > self::MAX_MACHINE_DEC || $this->machineId < 0) {
            throw new Exception('Illegal machine id.');
        }
    }

    /**
     * Create next ID.
     *
     * @return int
     * @throws \Exception
     */
    public function next()
    {
        $timestamp = $this->getMilliseconds();

        if ($timestamp < $this->_lastTimestamp) {
            throw new Exception('Clock error.');
        }

        if ($timestamp == $this->_lastTimestamp) {
            $this->_sequence = ++$this->_sequence & self::MAX_SEQUENCE_DEC;

            if ($this->_sequence == 0) {
                $timestamp = $this->waitTillNextMS($this->_lastTimestamp);
            }
        } else {
            $this->_sequence = 0;
        }

        $this->_lastTimestamp = $timestamp;

        return ($timestamp - self::EPOCH_TIME) << self::TIMESTAMP_OFFSET
            | $this->datacenterId << self::DATACENTER_OFFSET
            | $this->machineId << self::MACHINE_OFFSET
            | $this->_sequence;
    }

    /**
     * @return float
     */
    protected function getMilliseconds()
    {
        return floor(microtime(true) * 1000);
    }

    /**
     * @param $lastTimestamp
     * @return float
     */
    protected function waitTillNextMS($lastTimestamp)
    {
        do {
            $timestamp = $this->getMilliseconds();
        } while ($timestamp <= $lastTimestamp);

        return $timestamp;
    }
}