80-bit sequential unique identifier (as opposed to a 128-bit UUID)

snowflake.php

<?php

/**
 * Creates an 80-bit, binary(10) unique identifier.
 * 
 * Smaller, so indexes fit better in memory/RAM and the hex representation 
 * is still relatively URL friendly. Sequential, so inserts/indexes faster. 
 * (see https://www.percona.com/blog/2014/12/19/store-uuid-optimized-way/)
 *  
 * 4 bit worker id (supports 16 servers, from 0 to 15)
 * 60 bit timestamp
 * 16 bit random clock sequence
 * 
 * Here are some useful MySQL calls: 
 * SELECT DATE_FORMAT(FROM_UNIXTIME(CONV(SUBSTR(HEX(people.id), 2, 15),16,10)/10000000),'%d %b %Y %T:%f') FROM people; 
 **/
class Snowflake
{
    /**
     * Time (in 100ns steps) between the start of the UTC and Unix epochs
     * @var int
     */
    const INTERVAL = 0x01b21dd213814000;

    private $hex;

    public function __construct($hex = null, $worker = "0")
    {
        if (empty($hex)) {
            $hex = $this->makeHex($worker);
        }

        $this->hex = $hex;
    }

    public static function create($worker = "0")
    {
        return new Snowflake(null, $worker);
    }

    public static function createFromExisting($hex)
    {
        return new Snowflake($hex);
    }

    private function makeHex($worker)
    {
        // Convert decimal worker (0 to 15) to single digit hex (0 to F)
        $worker = dechex($worker);

        /** Get time since Gregorian calendar reform in 100ns intervals
         * This is exceedingly difficult because of PHP's (and pack()'s)
         * integer size limits.
         * Note that this will never be more accurate than to the microsecond.
         * You can also change the interval.
         */
        // $timestamp = microtime(1) * 10000000 + static::INTERVAL;
        $timestamp = microtime(1) * 10000000;

        // Convert to a string representation
        $timestamp = sprintf("%F", $timestamp);

        //strip decimal point
        preg_match("/^\d+/", $timestamp, $timestamp);

        // And now to a 64-bit binary representation that begins with the worker id
        $snowflake = base_convert($timestamp[0], 10, 16);
        $snowflake = str_pad($snowflake, 16, dechex($worker), STR_PAD_LEFT);

        // Generate a random clock sequence (2 bytes)
        $snowflake .= bin2hex(mcrypt_create_iv(2, MCRYPT_DEV_URANDOM));

        return $snowflake;
    }

    public function getHex(){
        return $this->hex;
    } 

    public function getDateTime($format = 'd M Y h:i:s A')
    {
        $timestamp = base_convert(substr($this->hex, 1, 15), 16, 10);
        $timestamp = sprintf("%d", $timestamp);
        // $timestamp = ($timestamp) / 10000000 - static::INTERVAL;
        $timestamp = ($timestamp) / 10000000;
        return date($format, $timestamp);
    }
    
}
 
$uid = Snowflake::create();
echo "Hex: ". $uid->getHex()."\n";         // Hex: 003349028aca2aca3642
echo "DateTime: " . $uid->getDateTime();   // DateTime: 29 Sep 2015 08:05:07 PM