ci框架源码阅读笔记2 一切的入口 index.php，ciindex.php
上一节（ci框架源码阅读笔记1 - 环境准备、基本术语和框架流程）中，我们提到了ci框架的基本流程，这里再次贴出流程图，以备参考：
作为CI框架的入口文件，源码阅读，自然由此开始。在源码阅读的过程中，我们并不会逐行进行解释，而只解释核心的功能和实现。
1. 设置应用程序环境
<span>define</span>('ENVIRONMENT', 'development');
这里的development可以是任何你喜欢的环境名称（比如dev,再如test），相对应的，你要在下面的switch case代码块中，对设定的环境做相关的错误控制，否则，CI框架会认为你没有配置好相应的环境，从而退出进程并给出对应的错误信息：
<span>default</span>: <span>exit</span>('The application environment is not set correctly.');
为什么一开始就要配置ENVIRONMENT？这是因为，CI框架中很多组件都依赖于ENVIRONMENT的配置，我们看一下system中，引用ENVIRONMENT的地方：
可以看到，很多组件都依赖于ENVIRONMENT.例如，查看system/config/Common.php, 这其中有一段引入配置文件的代码，是这样实现的：
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<span>if</span> ( ! <span>defined</span>('ENVIRONMENT') OR ! <span>file_exists</span>(<span>$file_path</span> = APPPATH.'config/'.ENVIRONMENT.'/config.php'<span>))
{
</span><span>$file_path</span> = APPPATH.'config/config.php'<span>;
}</span>
在CI框架中，很多配置文件都是通过这种方式引入的，因此ENVRIONMENT对于CI框架的正确运行时必须的，所以需要在开始的时候配置好ENVIRONMENT。设置ENVIRONMENT的一个好处是：可以很方便的切换系统的配置而不必修改系统代码。例如，在系统进入测试阶段时，database配置为测试的数据库，而在系统测试完毕时，database切换到线上的数据库。这好比是用一个开关控制了系统的环境切换，自然是非常方便的。
2. 配置系统目录和应用程序目录
CI框架允许你将系统核心源码和应用程序代码分开放置，但是你必须设定好系统的system文件夹和application文件夹（同样，文件夹名字可以是任何合法的文件夹名称，而不一定使用’system’和’application’）:
<span>$system_path</span> = 'system'<span>; </span><span>$application_folder</span> = 'application';
接下来，有这么一段代码：
<span>if</span> (<span>defined</span>('STDIN'<span>))
{
</span><span>chdir</span>(<span>dirname</span>(<span>__FILE__</span><span>));
}</span>
这段代码是干嘛的呢？首先，STDIN、STDOUT、STDERR是PHP以 CLI（Command Line Interface）模式运行而定义的三个常量，这三个常量类似于Shell的stdin,stdout,stdout,分别是PHP CLI模式下的标准输入、标准输出和标准错误流。也就是说，这三行代码是为了保证命令行模式下，CI框架可以正常运行。关于PHP CLI的更多细节可以参考：http://www.php-cli.com/
3. system目录的正确性验证和application目录验证
(1). system目录的正确性验证
Realpath返回的是目录或文件的绝对目录名（没有最后的/）
<span>if</span> (<span>realpath</span>(<span>$system_path</span>) !== <span>FALSE</span><span>)
{
</span><span>$system_path</span> = <span>realpath</span>(<span>$system_path</span>).'/'<span>;
}
</span><span>$system_path</span> = <span>rtrim</span>(<span>$system_path</span>, '/').'/'<span>;
</span><span>if</span> ( ! <span>is_dir</span>(<span>$system_path</span><span>))
{
</span><span>exit</span>("xxxxxxxx"<span>);
}</span>
几个定义的常量（PATH结尾的常量表示目录路径，DIR结尾的变量表示目录名）：
a. SELF（这里指index.php文件）
b. EXT(deprecated,废弃的，不必关注)
c. BASEPATH（system文件夹的路径）
d. FCPATH（前端控制器的路径）
e. SYSDIR（系统system目录名）
f. APPPATH（应用程序路径）
查看所有定义的常量的方法：
<span>Print_r</span>(<span>get_defined_constants</span>());
（2）application的目录验证。
代码较简单，不做过多的解释：
<span>if</span> (<span>is_dir</span>(<span>$application_folder</span><span>))
{
</span><span>define</span>('APPPATH', <span>$application_folder</span>.'/'<span>);
}
</span><span>else</span><span>
{
</span><span>if</span> ( ! <span>is_dir</span>(BASEPATH.<span>$application_folder</span>.'/'<span>))
{
</span><span>exit</span>("Your application folder path does not appear to be set correctly. Please open the following file and correct this: ".<span>SELF);
}
</span><span>define</span>('APPPATH', BASEPATH.<span>$application_folder</span>.'/'<span>);
}</span>
入口文件的最后一行，引入CodeIgniter.php（也是下一步阅读的关键）。CodeIgniter.php被称为bootstrap file，也就是它是一个引导文件，是CI框架执行流程的核心文件。
<span>require_once</span> BASEPATH.'core/CodeIgniter.php';
总结一下，index.php并没有做太多复杂的工作，而是类似一个后勤，为CI框架的运行提供了一系列配置参数和正确性验证，而这些配置和验证，是CI框架能够正常运行的关键。
最后，按照惯例，贴一下整个文件的源码（简化注释版）：
<span> 1</span> <?<span>php
</span><span> 2</span>
<span> 3</span> <span>define</span>('ENVIRONMENT', 'development'<span>);
</span><span> 4</span>
<span> 5</span> <span>if</span> (<span>defined</span>('ENVIRONMENT'<span>))
</span><span> 6</span> <span>{
</span><span> 7</span> <span>switch</span><span> (ENVIRONMENT)
</span><span> 8</span> <span> {
</span><span> 9</span> <span>case</span> 'development':
<span>10</span> <span>error_reporting</span>(<span>E_ALL</span><span>);
</span><span>11</span> <span>break</span><span>;
</span><span>12</span>
<span>13</span> <span>case</span> 'testing':
<span>14</span> <span>case</span> 'production':
<span>15</span> <span>error_reporting</span>(0<span>);
</span><span>16</span> <span>break</span><span>;
</span><span>17</span>
<span>18</span> <span>default</span>:
<span>19</span> <span>exit</span>('The application environment is not set correctly.'<span>);
</span><span>20</span> <span> }
</span><span>21</span> <span>}
</span><span>22</span>
<span>23</span> <span>/*</span>
<span>24</span> <span> * SYSTEM FOLDER NAME
</span><span>25</span> <span>*/</span>
<span>26</span> <span>$system_path</span> = 'system'<span>;
</span><span>27</span>
<span>28</span> <span>/*</span>
<span>29</span> <span> * APPLICATION FOLDER NAME
</span><span>30</span> <span>*/</span>
<span>31</span> <span>$application_folder</span> = 'application'<span>;
</span><span>32</span>
<span>33</span> <span>/*</span>
<span>34</span> <span> * Resolve the system path for increased reliability
</span><span>35</span> <span>*/</span>
<span>36</span> <span>if</span> (<span>defined</span>('STDIN'<span>))
</span><span>37</span> <span>{
</span><span>38</span> <span>chdir</span>(<span>dirname</span>(<span>__FILE__</span><span>));
</span><span>39</span> <span>}
</span><span>40</span>
<span>41</span> <span>if</span> (<span>realpath</span>(<span>$system_path</span>) !== <span>FALSE</span><span>)
</span><span>42</span> <span>{
</span><span>43</span> <span>$system_path</span> = <span>realpath</span>(<span>$system_path</span>).'/'<span>;
</span><span>44</span> <span>}
</span><span>45</span>
<span>46</span> <span>$system_path</span> = <span>rtrim</span>(<span>$system_path</span>, '/').'/'<span>;
</span><span>47</span>
<span>48</span> <span>if</span> ( ! <span>is_dir</span>(<span>$system_path</span><span>))
</span><span>49</span> <span>{
</span><span>50</span> <span>exit</span>("xxxxxxxx"<span>);
</span><span>51</span> <span>}
</span><span>52</span>
<span>53</span> <span>/*</span>
<span>54</span> <span> * set the main path constants
</span><span>55</span> <span>*/</span>
<span>56</span> <span>//</span><span> The name of THIS file</span>
<span>57</span> <span>define</span>('SELF', <span>pathinfo</span>(<span>__FILE__</span>,<span> PATHINFO_BASENAME));
</span><span>58</span>
<span>59</span> <span>//</span><span> this global constant is deprecataaed.</span>
<span>60</span> <span>define</span>('EXT', '.php'<span>);
</span><span>61</span>
<span>62</span> <span>//</span><span> Path to the system folder</span>
<span>63</span> <span>define</span>('BASEPATH', <span>str_replace</span>("\", "/", <span>$system_path</span><span>));
</span><span>64</span>
<span>65</span> <span>//</span><span> Path to the front controller (this file)</span>
<span>66</span> <span>define</span>('FCPATH', <span>str_replace</span>(SELF, '', <span>__FILE__</span><span>));
</span><span>67</span>
<span>68</span> <span>//</span><span> Name of the "system folder"</span>
<span>69</span> <span>define</span>('SYSDIR', <span>trim</span>(<span>strrchr</span>(<span>trim</span>(BASEPATH, '/'), '/'), '/'<span>));
</span><span>70</span>
<span>71</span> <span>//</span><span> The path to the "application" folder</span>
<span>72</span> <span>if</span> (<span>is_dir</span>(<span>$application_folder</span><span>))
</span><span>73</span> <span>{
</span><span>74</span> <span>define</span>('APPPATH', <span>$application_folder</span>.'/'<span>);
</span><span>75</span> <span>}
</span><span>76</span> <span>else</span>
<span>77</span> <span>{
</span><span>78</span> <span>if</span> ( ! <span>is_dir</span>(BASEPATH.<span>$application_folder</span>.'/'<span>))
</span><span>79</span> <span> {
</span><span>80</span> <span>exit</span>("Your application folder path does not appear to be set correctly. Please open the following file and correct this: ".<span>SELF);
</span><span>81</span> <span> }
</span><span>82</span>
<span>83</span> <span>define</span>('APPPATH', BASEPATH.<span>$application_folder</span>.'/'<span>);
</span><span>84</span> <span>}
</span><span>85</span>
<span>86</span> <span>require_once</span> BASEPATH.'core/CodeIgniter.php';
阁下需要在使用框架，那么就要把项目里的第一个程序都放在框架架构之中，而不能在根目录下新建一个admin.php。
阁下应该知晓，CI框架的入口文件是index.php，里面的任何页面都应该基于这个入口文件，即访问路径永远是index.php/*****这样的形式，而不能单独出来一个admin.php，这样的话，没有通过入口文件访问了，那么框架的效用也就没有了。
所以，阁下应该在application里的controllers目录下建一个admin.php，并按CI框架控制器的规则来使用它，这样，访问路径就是index.php/admin这样了
当然，阁下会以为所有的URL中都有一个index.php非常难看，那么阁下可以通过CI框架的路由规则将之隐藏掉，也可以使用服务器的伪静态功能来隐藏掉。但也仅是隐藏了而已，实际路径仍然有index.php这个入口文件。
1.修改Http.conf的LoadModule rewrite_module modules/mod_rewrite.so去掉注释 2.ci根目录增加.htaccess文件 RewriteEngine On RewriteBase /ci #Removes access to the system folder by users. #Additionally this will allow you to create a System.php controller, #previously this would not have been possible. #'system' can be replaced if you have renamed your system folder. RewriteCond %{REQUEST_URI} ^system.* RewriteRule ^(.*)$ /index.php?/$1 [L] #When your application folder isn't in the system folder #This snippet prevents user access to the application folder #Submitted by: Fabdrol #Rename 'application' to your applications folder name. RewriteCond %{REQUEST_URI} ^application.* RewriteRule ^(.*)$ /index.php?/$1 [L] #Checks to see if the user is attempting to access a valid file, #such as an image or css document, if this isn't true it sends the #request to index.php RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*)$ index.php?/$1 [L] # If we don't have mod_rewrite installed, all 404's # can be sent to index.php, and everything works as normal. # Submitted by: ElliotHaughin ErrorDocument 404 /index.php .htaccess文件内容
