在分布式系统中，需要生成全局UID的场合还是比较多的，twitter的snowflake解决了这种需求，实现也还是很简单的，除去配置信息，核心代码就是毫秒级时间41位+机器ID 10位+毫秒内序列12位。
twitter的分布式自增id算法snowflake，每秒能产生20w+的自增id，也适用于php。
<?php
2 class Idwork
3 {
4 const debug = 1;
5 static $workerId;
6 static $twepoch = 1361775855078;
7 static $sequence = 0;
8 const workerIdBits = 4;
9 static $maxWorkerId = 15;
10 const sequenceBits = 10;
11 static $workerIdShift = 10;
12 static $timestampLeftShift = 14;
13 static $sequenceMask = 1023;
14 private static $lastTimestamp = -1;
15
16 function __construct($workId){
17 if($workId > self::$maxWorkerId || $workId< 0 )
18 {
19 throw new Exception("worker Id can't be greater than 15 or less than 0");
20 }
21 self::$workerId=$workId;
22
23 echo 'logdebug->__construct()->self::$workerId:'.self::$workerId;
24 echo '</br>';
25
26 }
27
28 function timeGen(){
29 //获得当前时间戳
30 $time = explode(' ', microtime());
31 $time2= substr($time[0], 2, 3);
32 $timestramp = $time[1].$time2;
33 echo 'logdebug->timeGen()->$timestramp:'.$time[1].$time2;
34 echo '</br>';
35 return $time[1].$time2;
36 }
37 function tilNextMillis($lastTimestamp) {
38 $timestamp = $this->timeGen();
39 while ($timestamp <= $lastTimestamp) {
40 $timestamp = $this->timeGen();
41 }
42
43 echo 'logdebug->tilNextMillis()->$timestamp:'.$timestamp;
44 echo '</br>';
45 return $timestamp;
46 }
47
48 function nextId()
49 {
50 $timestamp=$this->timeGen();
51 echo 'logdebug->nextId()->self::$lastTimestamp1:'.self::$lastTimestamp;
52 echo '</br>';
53 if(self::$lastTimestamp == $timestamp) {
54 self::$sequence = (self::$sequence + 1) & self::$sequenceMask;
55 if (self::$sequence == 0) {
56 echo "###########".self::$sequenceMask;
57 $timestamp = $this->tilNextMillis(self::$lastTimestamp);
58 echo 'logdebug->nextId()->self::$lastTimestamp2:'.self::$lastTimestamp;
59 echo '</br>';
60 }
61 } else {
62 self::$sequence = 0;
63 echo 'logdebug->nextId()->self::$sequence:'.self::$sequence;
64 echo '</br>';
65 }
66 if ($timestamp < self::$lastTimestamp) {
67 throw new Excwption("Clock moved backwards. Refusing to generate id for ".(self::$lastTimestamp-$timestamp)." milliseconds");
68 }
69 self::$lastTimestamp = $timestamp;
70 echo 'logdebug->nextId()->self::$lastTimestamp3:'.self::$lastTimestamp;
71 echo '</br>';
72
73 echo 'logdebug->nextId()->(($timestamp - self::$twepoch << self::$timestampLeftShift )):'.((sprintf('%.0f', $timestamp) - sprintf('%.0f', self::$twepoch) ));
74 echo '</br>';
75 $nextId = ((sprintf('%.0f', $timestamp) - sprintf('%.0f', self::$twepoch) )) | ( self::$workerId << self::$workerIdShift ) | self::$sequence;
76 echo 'timestamp:'.$timestamp.'-----';
77 echo 'twepoch:'.sprintf('%.0f', self::$twepoch).'-----';
78 echo 'timestampLeftShift ='.self::$timestampLeftShift.'-----';
79 echo 'nextId:'.$nextId.'----';
80 echo 'workId:'.self::$workerId.'-----';
81 echo 'workerIdShift:'.self::$workerIdShift.'-----';
82 return $nextId;
83 }
84
85 }
86 $Idwork = new Idwork(1);
87 $a= $Idwork->nextId();
88 $Idwork = new Idwork(2);
89 $a= $Idwork->nextId();
90 ?>
