问题源自于深空博客的这篇文章《由会话重定向看到的对象销毁问题》，嗯，我以为这种问题早有人处理过了，因为2年前我就解决了此问题。解决办法已经发在phpchina.com的原创区：《关于PHP的Session处理的问题》。不过我在自己的博客上也发表同样的一篇帖子，留
问题源自于深空博客的这篇文章《由会话重定向看到的对象销毁问题》，嗯，我以为这种问题早有人处理过了，因为2年前我就解决了此问题。解决办法已经发在phpchina.com的原创区：《关于php的session处理的问题》。不过我在自己的博客上也发表同样的一篇帖子，留作备份。
在专家板块看到有人提出对Session处理机制的问题，原文《由会话重定向看到的对象销毁问题》。由于本人没有在专家板块发帖的资格，所以在这里发。
大概在08年年头我开始放弃Ruby on Rails转移到PHP开发，并以RoR的一些精神开发基于PHP的MVC框架，08年年底的时候，曾在phpchina这里发过一帖《自写MVC框架 Agi PHPMVC(核心)》，可以这么说，从我接触PHP以来一直是以自写的MVC框架在进行开发。目前该框架取名Agi on Rails，已经进入正式版的1.2版，下一个release版本将会考虑开源。该框架已经成功稳定的运行在多个Server Env(Windows、Linux，IIS、Apache、Lighttpd、Nginx)，开发过超过20个项目，承受过一天超过1200万PV的洗礼(预计并发峰值在200左右)。为何加这一个插曲，是为了强调，我是坚持将数据操作写在Model层的，而Session处理的逻辑，是被设计成一个 Model，而随着众多Model被Controler和View层调用。而开发者，是可以针对Session这个模块进行后期的高级的逻辑封装的。
废话就不多说了，解决方案如下：
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<p><span> 1</span> <span>//</span><span> 数据库连接的抽象层</span><span><br></span><span> 2</span> <span> </span><span>abstract</span><span>class</span><span> DB_Connector {<br></span><span> 3</span> <span> <br></span><span> 4</span> <span>protected</span><span>static</span><span><br></span><span> 5</span> <span>$_register</span><span>=</span><span>array</span><span>();<br></span><span> 6</span> <span><br></span><span> 7</span> <span>static</span><span>public</span><span>function</span><span> connect(</span><span>$anyKey</span><span>) {<br></span><span> 8</span> <span>//</span><span> 假设传入的$anyKey指定要使用MySQL进行连接<br></span><span> 9</span> <span> // 这中间的一些判断这里就忽略了</span><span><br></span><span>10</span> <span> </span><span>if</span><span> (</span><span>!</span><span>isset</span><span>(self</span><span>::</span><span>$_register</span><span>[</span><span>$anyKey</span><span>])) {<br></span><span>11</span> <span> self</span><span>::</span><span>$_register</span><span>[</span><span>$anyKey</span><span>] </span><span>=</span><span>new</span><span> DB_Connector_MySQL();<br></span><span>12</span> <span> }<br></span><span>13</span> <span>return</span><span> self</span><span>::</span><span>$_register</span><span>[</span><span>$anyKey</span><span>];<br></span><span>14</span> <span> }<br></span><span>15</span> <span><br></span><span>16</span> <span>static</span><span>public</span><span>function</span><span> disconnect(</span><span>$anyKey</span><span>) {<br></span><span>17</span> <span> self</span><span>::</span><span>connect(</span><span>$anyKey</span><span>)</span><span>-></span><span>disconnect();<br></span><span>18</span> <span> }<br></span><span>19</span> <span><br></span><span>20</span> <span>static</span><span>public</span><span>function</span><span> handleDisconnect(</span><span>$anyKey</span><span>) {<br></span><span>21</span> <span> self</span><span>::</span><span>connect(</span><span>$anyKey</span><span>)</span><span>-></span><span>handleDisconnect();<br></span><span>22</span> <span> }<br></span><span>23</span> <span>}<br></span><span>24</span> <span><br></span><span>25</span> <span> </span><span>//</span><span> 数据库连接的驱动层</span><span><br></span><span>26</span> <span> </span><span>class</span><span> DB_Connector_MySQL {<br></span><span>27</span> <span> <br></span><span>28</span> <span>protected</span><span><br></span><span>29</span> <span>$_connector</span><span>=</span><span>null</span><span>,</span><span><br></span><span>30</span> <span>$_isHandleDisconnect</span><span>=</span><span>false</span><span>;<br></span><span>31</span> <span><br></span><span>32</span> <span>public</span><span>function</span><span> __construct() {<br></span><span>33</span> <span>//</span><span> 执行具体的连接</span><span><br></span><span>34</span> <span> </span><span>$this</span><span>-></span><span>_connector </span><span>=</span><span>new</span><span> MySQLDriver();<br></span><span>35</span> <span> }<br></span><span>36</span> <span> <br></span><span>37</span> <span>public</span><span>function</span><span> __destruct() {<br></span><span>38</span> <span>if</span><span> (</span><span>!</span><span>$this</span><span>-></span><span>_isHandleDisconnect)<br></span><span>39</span> <span>$this</span><span>-></span><span>disconnect();<br></span><span>40</span> <span> }<br></span><span>41</span> <span><br></span><span>42</span> <span>public</span><span>function</span><span> disconnect() {<br></span><span>43</span> <span>$this</span><span>-></span><span>_connector </span><span>=</span><span>null</span><span>;<br></span><span>44</span> <span> }<br></span><span>45</span> <span><br></span><span>46</span> <span>public</span><span>function</span><span> handleDisconnect() {<br></span><span>47</span> <span>$this</span><span>-></span><span>_isHandleDisconnect </span><span>=</span><span>true</span><span>;<br></span><span>48</span> <span> }<br></span><span>49</span> <span>}<br></span><span>50</span> <span><br></span><span>51</span> <span> </span><span>//</span><span> Session的实现层<br></span><span>52</span> <span>// Any_ActiveRecord是Model的抽象层，这里就不实现了</span><span><br></span><span>53</span> <span> </span><span>class</span><span> Session </span><span>extends</span><span> Any_ActiveRecord {<br></span><span>54</span> <span> <br></span><span>55</span> <span>protected</span><span>static</span><span><br></span><span>56</span> <span>$_connectorKey</span><span>=</span><span>'</span><span>Any</span><span>'</span><span>;<br></span><span>57</span> <span><br></span><span>58</span> <span>//</span><span> 标准实现</span><span><br></span><span>59</span> <span>static</span><span>public</span><span>function</span><span> open() {<br></span><span>60</span> <span>//</span><span> 一旦将Session处理转移给DB层面去控制<br></span><span>61</span> <span> // 就意味着数据库连接的释放，也必须转交给这个Session模块来处理</span><span><br></span><span>62</span> <span> DB_Connector</span><span>::</span><span>handleDisconnect(self</span><span>::</span><span>$_connectorKey</span><span>);<br></span><span>63</span> <span>//</span><span> 其他启动配置，包括Session GC清理的基数等等</span><span><br></span><span>64</span> <span> }<br></span><span>65</span> <span> <br></span><span>66</span> <span>//</span><span> 标准实现<br></span><span>67</span> <span> // </span><span><br></span><span>68</span> <span>static</span><span>public</span><span>function</span><span> pick(</span><span>$sId</span><span>) {<br></span><span>69</span> <span> <br></span><span>70</span> <span> }<br></span><span>71</span> <span><br></span><span>72</span> <span>//</span><span> 标准实现</span><span><br></span><span>73</span> <span>static</span><span>public</span><span>function</span><span> dump(</span><span>$sId</span><span>,</span><span>$val</span><span>) {<br></span><span>74</span> <span> <br></span><span>75</span> <span> }<br></span><span>76</span> <span><br></span><span>77</span> <span>//</span><span> 标准实现</span><span><br></span><span>78</span> <span>static</span><span>public</span><span>function</span><span> destroy(</span><span>$sId</span><span>) {<br></span><span>79</span> <span> <br></span><span>80</span> <span> }<br></span><span>81</span> <span><br></span><span>82</span> <span>//</span><span> 标准实现</span><span><br></span><span>83</span> <span>static</span><span>public</span><span>function</span><span> gc() {<br></span><span>84</span> <span> <br></span><span>85</span> <span> }<br></span><span>86</span> <span><br></span><span>87</span> <span>//</span><span> 标准实现</span><span><br></span><span>88</span> <span>static</span><span>public</span><span>function</span><span> close() {<br></span><span>89</span> <span>//</span><span> 一切OK，再由Session Close的时候，释放数据库连接</span><span><br></span><span>90</span> <span> DB_Connector</span><span>::</span><span>disconnect(self</span><span>::</span><span>$_connectorKey</span><span>);<br></span><span>91</span> <span> }<br></span><span>92</span> <span>}</span></p>至此，第一个问题解决了，就是关于数据库连接的释放问题。但是这里存在第二个问题(假如你在使用的框架，取出的Session是一个数组，或者你直接就取出的是一个数组，可以忽略第二个问题)，就是按照常理，一个Session经由Model取出，理应被是一个Session的实例，然后，由于PHP本身的运行机制的问题，变量的释放，往往早于Session的注销。这时就要发挥出OO的本色了：
根据上述的Session类，我们进行一点点改造：
<p><span> 1</span> <span>//</span><span> Session的实现层<br></span><span> 2</span> <span>// Any_ActiveRecord是Model的抽象层，这里就不实现了</span><span><br></span><span> 3</span> <span>class</span><span> Session </span><span>extends</span><span> Any_ActiveRecord {<br></span><span> 4</span> <span> <br></span><span> 5</span> <span>protected</span><span>static</span><span><br></span><span> 6</span> <span>$_connectorKey</span><span>=</span><span>'</span><span>Any</span><span>'</span><span>,</span><span><br></span><span> 7</span> <span>$_currSess</span><span>=</span><span>null</span><span>;<br></span><span> 8</span> <span><br></span><span> 9</span> <span>//</span><span> 标准实现</span><span><br></span><span>10</span> <span>static</span><span>public</span><span>function</span><span> open() {<br></span><span>11</span> <span>//</span><span> 一旦将Session处理转移给DB层面去控制<br></span><span>12</span> <span> // 就意味着数据库连接的释放，也必须转交给这个Session模块来处理</span><span><br></span><span>13</span> <span> DB_Connector</span><span>::</span><span>handleDisconnect(self</span><span>::</span><span>$_connectorKey</span><span>);<br></span><span>14</span> <span>//</span><span> 其他启动配置，包括Session GC清理的基数等等</span><span><br></span><span>15</span> <span> }<br></span><span>16</span> <span> <br></span><span>17</span> <span>//</span><span> 标准实现<br></span><span>18</span> <span> // 拿出Session</span><span><br></span><span>19</span> <span>static</span><span>public</span><span>function</span><span> pick(</span><span>$sId</span><span>) {<br></span><span>20</span> <span> self</span><span>::</span><span>$_currSess</span><span>=</span><span> self</span><span>::</span><span>find_by_sess_id(</span><span>$sId</span><span>);<br></span><span>21</span> <span>if</span><span> (</span><span>!</span><span>self</span><span>::</span><span>$_currSess</span><span>-></span><span>isEmpty())<br></span><span>22</span> <span>return</span><span> self</span><span>::</span><span>$_currSess</span><span>-></span><span>value;<br></span><span>23</span> <span>return</span><span>false</span><span>;<br></span><span>24</span> <span> }<br></span><span>25</span> <span><br></span><span>26</span> <span>//</span><span> 标准实现</span><span><br></span><span>27</span> <span>static</span><span>public</span><span>function</span><span> dump(</span><span>$sId</span><span>,</span><span>$val</span><span>) {<br></span><span>28</span> <span>//</span><span> 新访客</span><span><br></span><span>29</span> <span>if</span><span> (self</span><span>::</span><span>$_currSess</span><span>-></span><span>isEmpty())<br></span><span>30</span> <span> self</span><span>::</span><span>$_currSess</span><span>-></span><span>sess_id </span><span>==</span><span>$sId</span><span>;<br></span><span>31</span> <span> self</span><span>::</span><span>$_currSess</span><span>-></span><span>value </span><span>=</span><span>$val</span><span>;<br></span><span>32</span> <span> self</span><span>::</span><span>$_currSess</span><span>-></span><span>save();<br></span><span>33</span> <span> }<br></span><span>34</span> <span><br></span><span>35</span> <span>//</span><span> 标准实现</span><span><br></span><span>36</span> <span>static</span><span>public</span><span>function</span><span> destroy(</span><span>$sId</span><span>) {<br></span><span>37</span> <span> <br></span><span>38</span> <span> }<br></span><span>39</span> <span><br></span><span>40</span> <span>//</span><span> 标准实现</span><span><br></span><span>41</span> <span>static</span><span>public</span><span>function</span><span> gc() {<br></span><span>42</span> <span> <br></span><span>43</span> <span> }<br></span><span>44</span> <span><br></span><span>45</span> <span>//</span><span> 标准实现</span><span><br></span><span>46</span> <span>static</span><span>public</span><span>function</span><span> close() {<br></span><span>47</span> <span>//</span><span> 一切OK，再由Session Close的时候，释放数据库连接</span><span><br></span><span>48</span> <span> DB_Connector</span><span>::</span><span>disconnect(self</span><span>::</span><span>$_connectorKey</span><span>);<br></span><span>49</span> <span> self</span><span>::</span><span>$_currSess</span><span>=</span><span>null</span><span>;<br></span><span>50</span> <span> }<br></span><span>51</span> <span>}</span></p>好了，大功告成！原理就不多说了，多做点测试吧。
将Session写成Model的好处是，可以有针对性的进行单元测试。也许有用户会担心，你把Session放在数据库层，能承受得多大的并发量呢？
OK，我可以给出一些实际数据，一个投票的程序，PHP和MySQL跑在同一台服务器(Server系统是Ubuntu Server以Lighttpd，已经通过压力测试优化过fastcgi线程数字)上，3天收集有效投票记录总数900万+(注意，有效投票是指限制ip的，每一票都要检查ip和该ip上一次投票的时间)，Session使用Model操作，以MyISAM引擎存放在MySQL的表中，Session主键已经刷到8位数。最高峰一天PV 1200万。
另：我发现cnblogs的源代码极其以及十分之丑陋，无法让人家复制代码，提供附件下载。
