通过分析WP的代码来学习PHP。1

浏览数：78 / 时间：2015年06月09日

下载了WP的代码，并且应用到了网站上面，现在也在正常的运行中，地址是：www.freealgorithm.tk 。具体的申请过程就不赘述了，学习WP的代码。

他的目录结构就不看了，可以下载同名文件我会通过相对目录来区分。

进入网站的第一个默认的页面：/index.php

<?php

/**
 * Front to the WordPress application. This file doesn‘t do anything, but loads
 * wp-blog-header.php which does and tells WordPress to load the theme.
 *
 * @package WordPress
 */

/**
 * Tells WordPress to load the WordPress theme and output it.
 *
 * @var bool
 
*/

define(‘WP_USE_THEMES‘, true);

/** Loads the WordPress Environment and Template */
 #定义WP_USE_THEMES为true
require( dirname( __FILE__ ) . ‘/wp-blog-header.php‘ );
 #返回路径中目录部分并且连接字符串得到此php文件的位置，用这个文件代替这个位置
#引入同目录下的wp-blog-header.php文件

知识点：define函数，bool define ( string $name , mixed $value [, bool $case_insensitive = false ] ) 成功返回true否则false。
name：常量的名字。value：常量的值；仅允许标量和 null。标量的类型是 integer，float，string 或者 boolean。也能够定义常量值的类型为 resource ，但并不推荐这么做，可能会导致未知状况的发生。

require函数替换参数指向的文件，__FILE__取得当前文件的绝对路径，dirname返回路径中的目录部分。比如这个文件返回的就是根目录/。‘.‘这个符号是字符串连接运算符，将dirname(__FILE__)返回的字符串与‘/wp-blog-header.php‘相连接然后require进去。

而/wp-blog-header.php这个文件被包含了，如下：

 1 <?php
 2 
 3 /**
 4  * Loads the WordPress environment and template.
 5  载入WordPress的环境和模板*
 6  * @package WordPress
 7  */
 8 
 9 
10 if ( !isset($wp_did_header) ) #变量是否定义，定义返回true
11 {
12 
13     $wp_did_header = true;
14 
15 
16     require_once( dirname(__FILE__) . ‘/wp-load.php‘ );
17 
18     #用wp-load.php代替此语句
19     /*如果定义了就不继续执行，否则执行下面的语句    */
20 
21     wp();
22 
23 
24     require_once( ABSPATH . WPINC . ‘/template-loader.php‘ );
25 
26 #同样用
27 }

isset函数用来判断这个变量是否已经被定义了，如果定义了就返回true否则返回false。如果没有定义的话就执行下面的语句，$wp_did_header=true;是定义变量，他是一个布尔变量。然后require_once这个文件 ,require_once函数与require的区别是以后再这个文件里不能再包含这个文件了，即仅仅包含这个文件一次。这些的动作是定义一个布尔变量且包含一个文件。下面的wp();函数指行，现在不知道这个函数的作用，一会就会看到。然后继续包含ABSPATH.WPINC.‘/template-loader.php‘。这个文件了。ABSPATH是绝对路径的意思，这个是WP自定义的常量，还有WPINC这两个，现在我们也不知道它的值是什么。此文件到此没有结束，我们继续跟踪进入wp-load.php.

 1 <?php
 2 
 3 /**
 4 
 5  * Bootstrap file for setting the ABSPATH constant
 6  * and loading the wp-config.php file. The wp-config.php
 7  * file will then load the wp-settings.php file, which
 8  * will then set up the WordPress environment.
 9  *
10  * If the wp-config.php file is not found then an error
11  * will be displayed asking the visitor to set up the
12  * wp-config.php file.
13  *
14  * Will also search for wp-config.php in WordPress‘ parent
15  * directory to allow the WordPress directory to remain
16  * untouched.
17  *
18  * @internal This file must be parsable by PHP4.
19  *
20  * @package WordPress
21  */
22 
23 
24 /** Define ABSPATH as this file‘s directory 
25 */
26 
27 define( ‘ABSPATH‘, dirname(__FILE__) . ‘/‘ );
28 
29 
30 error_reporting( E_CORE_ERROR | E_CORE_WARNING | E_COMPILE_ERROR | E_ERROR | E_WARNING | E_PARSE | E_USER_ERROR | E_USER_WARNING | E_RECOVERABLE_ERROR );
31 
32 /*error_reporting() 函数能够在运行时设置 error_reporting 指令。 PHP 有诸多错误级别，使用该函数可以设置在脚本运行时的级别。 如果没有设置可选参数 level， error_reporting() 仅会返回当前的错误报告级别。 */
33 
34 if ( file_exists( ABSPATH . ‘wp-config.php‘) ) #file_exists — 检查文件或目录是否存在，绝对路径+‘wp-config.php‘检测是否存在，这个文件是设置文件，后来在网站文件上传完成后进行安装时候来创建，所以在没有安装时候是不存在这个文件的。
35 {
36 
37     /** The config file resides in ABSPATH */
38     
39     require_once( ABSPATH . ‘wp-config.php‘ );
40 
41 #如果文件存在，require_once把文件拿来
42 #如果文件不存在，判断绝对路径取
43 
44 } elseif ( file_exists( dirname(ABSPATH) . ‘/wp-config.php‘ ) && ! file_exists( dirname(ABSPATH) . ‘/wp-settings.php‘ ) ) 
45 {
46 
47     /** The config file resides one level above ABSPATH but is not part of another install */
48 
49     require_once( dirname(ABSPATH) . ‘/wp-config.php‘ );
50 
51 
52 } else {
53 
54     // A config file doesn‘t exist
55 
56 
57     define( ‘WPINC‘, ‘wp-includes‘ );
58 
59     define( ‘WP_CONTENT_DIR‘, ABSPATH . ‘wp-content‘ );
60 
61     require_once( ABSPATH . WPINC . ‘/load.php‘ );
62 
63     require_once( ABSPATH . WPINC . ‘/version.php‘ );
64 
65 
66     wp_check_php_mysql_versions();
67 
68     wp_load_translations_early();
69 
70     // Standardize $_SERVER variables across setups.
71     
72     wp_fix_server_vars();
73 
74 
75     require_once( ABSPATH . WPINC . ‘/functions.php‘ );
76 
77 
78     $path = wp_guess_url() . ‘/wp-admin/setup-config.php‘;
79 
80     // Die with an error message
81 
82     $die  = __( "There doesn‘t seem to be a <code>wp-config.php</code> file. I need this before we can get started." ) . ‘</p>‘;
83 
84     $die .= ‘<p>‘ . __( "Need more help? <a href=‘http://codex.wordpress.org/Editing_wp-config.php‘>We got it</a>." ) . ‘</p>‘;
85 
86     $die .= ‘<p>‘ . __( "You can create a <code>wp-config.php</code> file through a web interface, but this doesn‘t work for all server setups. The safest way is to manually create the file." ) . ‘</p>‘;
87     $die .= ‘<p><a href="‘ . $path . ‘" class="button button-large">‘ . __( "Create a Configuration File" ) . ‘</a>‘;
88 
89 
90     wp_die( $die, __( ‘WordPress &rsaquo; Error‘ ) );
91 }

代码稍长，但是以后的代码会更长。这里看到了他的注释说定义ABSPATH为当前文件的目录，而且看到了这个define语句，知道了ABSPATH是dirname(__FILE__).‘/‘。其实还是这个根目录。error_reporting函数的说明在代码里面注释着意思是定义错误级别，我在书中也没有看到类似的说明这个函数，现在不予理会。
if当前绝对路径下的 /wp-config.php文件存在的话就require这个文件。不存在的话继续判断（/wp-config.php和/wp-settings.php）文件是否不存在，那么判断wp-config.php这个文件的判断是否多余？wp-setting.php这个文件是存在的，而wp-config.php是后来在安装时后生成的，第一次安装使用时候是没有的。否则就定义WPINC为‘wp-includes‘，define( ‘WP_CONTENT_DIR‘, ABSPATH . ‘wp-content‘ );require_once( ABSPATH . WPINC . ‘/load.php‘ );这句是将 /wp-includes/load.php包含进去，require_once( ABSPATH . WPINC . ‘/version.php‘ );这句将/wp-includes/version.php包含进去。先跟踪进去/wp-includes/load.php。

  1 <?php
  2 
  3 /**
  4  * These functions are needed to load WordPress.
  5  *
  6  * @internal This file must be parsable by PHP4.
  7  *
  8  * @package WordPress
  9  */
 10 
 11 
 12 /**
 13  * Turn register globals off.
 14  *
 15  * @access private
 16  * @since 2.1.0
 17  * @return null Will return null if register_globals PHP directive was disabled
 18  */
 19 
 20 function wp_unregister_GLOBALS() 
 21 {
 22 
 23     if ( !ini_get( ‘register_globals‘ ) )
 24 
 25         return;
 26 
 27 
 28     if ( isset( $_REQUEST[‘GLOBALS‘] ) )
 29 
 30         die( ‘GLOBALS overwrite attempt detected‘ );
 31 
 32     // Variables that shouldn‘t be unset
 33 
 34     $no_unset = array( ‘GLOBALS‘, ‘_GET‘, ‘_POST‘, ‘_COOKIE‘, ‘_REQUEST‘, ‘_SERVER‘, ‘_ENV‘, ‘_FILES‘, ‘table_prefix‘ );
 35 
 36 
 37     $input = array_merge( $_GET, $_POST, $_COOKIE, $_SERVER, $_ENV, $_FILES, isset( $_SESSION ) && is_array( $_SESSION ) ? $_SESSION : array() );
 38     foreach ( $input as $k => $v )
 39 
 40         if ( !in_array( $k, $no_unset ) && isset( $GLOBALS[$k] ) ) 
 41         {
 42 
 43             unset( $GLOBALS[$k] );
 44 
 45         }
 46 
 47 }
 48 
 49 
 50 /**
 51  * Fix $_SERVER variables for various setups.
 52  *
 53  * @access private
 54  * @since 3.0.0
 55  */
 56 
 57 function wp_fix_server_vars() 
 58 {
 59 
 60     global $PHP_SELF;
 61 
 62 
 63     $default_server_values = array(
 64 
 65         ‘SERVER_SOFTWARE‘ => ‘‘,
 66 
 67         ‘REQUEST_URI‘ => ‘‘,
 68 
 69     );
 70 
 71 
 72     $_SERVER = array_merge( $default_server_values, $_SERVER );
 73 
 74     // Fix for IIS when running with PHP ISAPI
 75 
 76     if ( empty( $_SERVER[‘REQUEST_URI‘] ) || ( php_sapi_name() != ‘cgi-fcgi‘ && preg_match( ‘/^Microsoft-IIS\//‘, $_SERVER[‘SERVER_SOFTWARE‘] ) ) )
 77     {
 78 
 79         // IIS Mod-Rewrite
 80 
 81         if ( isset( $_SERVER[‘HTTP_X_ORIGINAL_URL‘] ) )
 82         {
 83 
 84             $_SERVER[‘REQUEST_URI‘] = $_SERVER[‘HTTP_X_ORIGINAL_URL‘];
 85 
 86         }
 87         // IIS Isapi_Rewrite
 88 
 89         else if ( isset( $_SERVER[‘HTTP_X_REWRITE_URL‘] ) ) {
 90 
 91             $_SERVER[‘REQUEST_URI‘] = $_SERVER[‘HTTP_X_REWRITE_URL‘];
 92 
 93         } else {
 94             // Use ORIG_PATH_INFO if there is no PATH_INFO
 95 
 96             if ( !isset( $_SERVER[‘PATH_INFO‘] ) && isset( $_SERVER[‘ORIG_PATH_INFO‘] ) )
 97 
 98                 $_SERVER[‘PATH_INFO‘] = $_SERVER[‘ORIG_PATH_INFO‘];
 99 
100 
101             // Some IIS + PHP configurations puts the script-name in the path-info (No need to append it twice)
102 
103             if ( isset( $_SERVER[‘PATH_INFO‘] ) ) {
104 
105                 if ( $_SERVER[‘PATH_INFO‘] == $_SERVER[‘SCRIPT_NAME‘] )
106 
107                     $_SERVER[‘REQUEST_URI‘] = $_SERVER[‘PATH_INFO‘];
108 
109                 else
110 
111                     $_SERVER[‘REQUEST_URI‘] = $_SERVER[‘SCRIPT_NAME‘] . $_SERVER[‘PATH_INFO‘];
112                         }    
113     
114 
115             // Append the query string if it exists and isn‘t null
116 
117             if ( ! empty( $_SERVER[‘QUERY_STRING‘] ) ) {
118 
119                 $_SERVER[‘REQUEST_URI‘] .= ‘?‘ . $_SERVER[‘QUERY_STRING‘];
120 
121             }
122 
123         }
124 
125     }
126 
127 
128     // Fix for PHP as CGI hosts that set SCRIPT_FILENAME to something ending in php.cgi for all requests
129     
130     if ( isset( $_SERVER[‘SCRIPT_FILENAME‘] ) && ( strpos( $_SERVER[‘SCRIPT_FILENAME‘], ‘php.cgi‘ ) == strlen( $_SERVER[‘SCRIPT_FILENAME‘] ) - 7 ) )
131 
132         $_SERVER[‘SCRIPT_FILENAME‘] = $_SERVER[‘PATH_TRANSLATED‘];
133 
134     // Fix for Dreamhost and other PHP as CGI hosts
135 
136     if ( strpos( $_SERVER[‘SCRIPT_NAME‘], ‘php.cgi‘ ) !== false )
137 
138         unset( $_SERVER[‘PATH_INFO‘] );
139 
140     // Fix empty PHP_SELF
141 
142     $PHP_SELF = $_SERVER[‘PHP_SELF‘];
143 
144     if ( empty( $PHP_SELF ) )
145 
146         $_SERVER[‘PHP_SELF‘] = $PHP_SELF = preg_replace( ‘/(\?.*)?$/‘, ‘‘, $_SERVER["REQUEST_URI"] );
147 
148 }
149 
150 
151 /**
152  * Check for the required PHP version, and the MySQL extension or a database drop-in.
153  *
154  * Dies if requirements are not met.
155  *
156  * @access private
157  * @since 3.0.0
158  */
159 
160 
161 function wp_check_php_mysql_versions() {
162 
163     global $required_php_version, $wp_version;
164 
165     $php_version = phpversion();
166 
167     if ( version_compare( $required_php_version, $php_version, ‘>‘ ) ) {
168 
169         wp_load_translations_early();
170 
171         header( ‘Content-Type: text/html; charset=utf-8‘ );
172 
173         die( sprintf( __( ‘Your server is running PHP version %1$s but WordPress %2$s requires at least %3$s.‘ ), $php_version, $wp_version, $required_php_version ) );
174 
175     }
176 
177 
178     if ( ! extension_loaded( ‘mysql‘ ) && ! extension_loaded( ‘mysqli‘ ) && ! file_exists( WP_CONTENT_DIR . ‘/db.php‘ ) ) {
179 
180         wp_load_translations_early();
181 
182         header( ‘Content-Type: text/html; charset=utf-8‘ );
183 
184         die( __( ‘Your PHP installation appears to be missing the MySQL extension which is required by WordPress.‘ ) );
185 
186     }
187 
188 }
189 
190 
191 
192 /**
193  * Don‘t load all of WordPress when handling a favicon.ico request.
194  * Instead, send the headers for a zero-length favicon and bail.
195  *
196  * @since 3.0.0
197  */
198 
199 
200 function wp_favicon_request() {
201 
202     if ( ‘/favicon.ico‘ == $_SERVER[‘REQUEST_URI‘] ) {
203 
204         header(‘Content-Type: image/vnd.microsoft.icon‘);
205 
206         header(‘Content-Length: 0‘);
207 
208         exit;
209 
210     }
211 
212 }
213 
214 
215 /**
216  * Dies with a maintenance message when conditions are met.
217  *
218  * Checks for a file in the WordPress root directory named ".maintenance".
219  * This file will contain the variable $upgrading, set to the time the file
220  * was created. If the file was created less than 10 minutes ago, WordPress
221  * enters maintenance mode and displays a message.
222  *
223  * The default message can be replaced by using a drop-in (maintenance.php in
224  * the wp-content directory).
225  *
226  * @access private
227  * @since 3.0.0
228  */
229 
230 
231 function wp_maintenance() {
232 
233     if ( !file_exists( ABSPATH . ‘.maintenance‘ ) || defined( ‘WP_INSTALLING‘ ) )
234 
235         return;
236 
237 
238     global $upgrading;
239 
240 
241     include( ABSPATH . ‘.maintenance‘ );
242 
243     // If the $upgrading timestamp is older than 10 minutes, don‘t die.
244 
245     if ( ( time() - $upgrading ) >= 600 )
246 
247         return;
248 
249 
250     if ( file_exists( WP_CONTENT_DIR . ‘/maintenance.php‘ ) ) {
251 
252         require_once( WP_CONTENT_DIR . ‘/maintenance.php‘ );
253 
254         die();
255 
256     }
257 
258 
259     wp_load_translations_early();
260 
261 
262     $protocol = $_SERVER["SERVER_PROTOCOL"];
263 
264     if ( ‘HTTP/1.1‘ != $protocol && ‘HTTP/1.0‘ != $protocol )
265 
266         $protocol = ‘HTTP/1.0‘;
267 
268     header( "$protocol 503 Service Unavailable", true, 503 );
269 
270     header( ‘Content-Type: text/html; charset=utf-8‘ );
271 
272     header( ‘Retry-After: 600‘ );
273 
274 ?>