php 使用redis锁限制并发访问类

1.并发访问限制问题

对于一些需要限制同一个用户并发访问的场景，如果用户并发请求多次，而服务器处理没有加锁限制，用户则可以多次请求成功。

例如换领优惠券，如果用户同一时间并发提交换领码，在没有加锁限制的情况下，用户则可以使用同一个换领码同时兑换到多张优惠券。

伪代码如下：

<code class="hljs scss has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">if <span class="hljs-function" style="box-sizing: border-box;">A(可以换领)</span>    <span class="hljs-function" style="box-sizing: border-box;">B(执行换领)</span>    <span class="hljs-function" style="box-sizing: border-box;">C(更新为已换领)</span><span class="hljs-function" style="box-sizing: border-box;">D(结束)</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

如果用户并发提交换领码，都能通过可以换领(A)的判断，因为必须有一个执行换领(B)后，才会更新为已换领(C)。因此如果用户在有一个更新为已换领之前，有多少次请求，这些请求都可以执行成功。 

2.并发访问限制方法

使用文件锁可以实现并发访问限制，但对于分布式架构的环境，使用文件锁不能保证多台服务器的并发访问限制。

Redis是一个开源的使用ANSI C语言编写、支持网络、可基于内存亦可持久化的日志型、Key-Value数据库，并提供多种语言的API。 
本文将使用其setnx方法实现分布式锁功能。setnx即Set it N**ot eX**ists。 
当键值不存在时，插入成功（获取锁成功），如果键值已经存在，则插入失败（获取锁失败）

RedisLock.class.php

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><?php<span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** *  Redis锁操作类 *  Date:   2016-06-30 *  Author: fdipzone *  Ver:    1.0 * *  Func: *  public  lock    获取锁 *  public  unlock  释放锁 *  private connect 连接 */</span>class RedisLock { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// class start</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> $_config;    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> $_redis;    <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 初始化     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> Array $config redis连接设定     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> function <span class="hljs-title" style="box-sizing: border-box;">__construct</span>($config=array()){        $<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_config = $config;        $<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_redis = $<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->connect();    }    <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 获取锁     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span>  String  $key    锁标识     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span>  Int     $expire 锁过期时间     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @return</span> Boolean     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> function <span class="hljs-title" style="box-sizing: border-box;">lock</span>($key, $expire=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>){        $is_lock = $<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_redis->setnx($key, time()+$expire);        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 不能获取锁</span>        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(!$is_lock){            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 判断锁是否过期</span>            $lock_time = $<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_redis->get($key);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 锁已过期，删除锁，重新获取</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(time()>$lock_time){                $<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->unlock($key);                $is_lock = $<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_redis->setnx($key, time()+$expire);            }        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> $is_lock? <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span> : <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>;    }    <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 释放锁     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span>  String  $key 锁标识     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @return</span> Boolean     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> function <span class="hljs-title" style="box-sizing: border-box;">unlock</span>($key){        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> $<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_redis->del($key);    }    <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**     * 创建redis连接     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @return</span> Link     */</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> function <span class="hljs-title" style="box-sizing: border-box;">connect</span>(){        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span>{            $redis = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Redis();            $redis->connect($<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_config[<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'host'</span>],$<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_config[<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'port'</span>],$<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_config[<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'timeout'</span>],$<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_config[<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'reserved'</span>],$<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_config[<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'retry_interval'</span>]);            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(empty($<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_config[<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'auth'</span>])){                $redis->auth($<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_config[<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'auth'</span>]);            }            $redis->select($<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>->_config[<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'index'</span>]);        }<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span>(RedisException $e){            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Exception($e->getMessage());            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>;        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> $redis;    }} <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// class end</span>?></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li><li style="box-sizing: border-box; padding: 0px 5px;">81</li><li style="box-sizing: border-box; padding: 0px 5px;">82</li></ul>

demo.php

<code class="hljs php has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"><?php</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">require</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'RedisLock.class.php'</span>;<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$config</span> = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">array</span>(    <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'host'</span> => <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'localhost'</span>,    <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'port'</span> => <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6379</span>,    <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'index'</span> => <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>,    <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'auth'</span> => <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">''</span>,    <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'timeout'</span> => <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>,    <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'reserved'</span> => <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">NULL</span>,    <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'retry_interval'</span> => <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>,);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 创建redislock对象</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$oRedisLock</span> = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RedisLock(<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$config</span>);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 定义锁标识</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$key</span> = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'mylock'</span>;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 获取锁</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$is_lock</span> = <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$oRedisLock</span>->lock(<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$key</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$is_lock</span>){    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">echo</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'get lock success<br>'</span>;    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">echo</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'do sth..<br>'</span>;    sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>);    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">echo</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'success<br>'</span>;    <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$oRedisLock</span>->unlock(<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$key</span>);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 获取锁失败</span>}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span>{    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">echo</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'request too frequently<br>'</span>;}<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">?></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li></ul>

测试方法： 
打开两个不同的浏览器,同时在A,B中访问demo.php 
如果先访问的会获取到锁 
输出 
get lock success 
do sth.. 
success

另一个获取锁失败则会输出request too frequently

保证同一时间只有一个访问有效，有效限制并发访问。 


为了避免系统突然出错导致死锁，所以在获取锁的时候增加一个过期时间，如果已超过过期时间，即使是锁定状态都会释放锁，避免死锁导致的问题。 


源码下载地址：点击查看