文件位置：Location: ./system/core/Common.php
CodeIgniter 使用了一些全局定义的函数来完成操作，在任何情况下你都能够使用这些函数。使用他们不需要载入任何类库或辅助函数。
这些函数主要用于加载基类和执行请求。
1、 第一个函数is_php
判断当前php版本是否大于指定的php版本，有些地方需要用到这个函数
2、 判断文件夹是否有可写权限is_really_writable()
因为函数is_writable()在window和unix中并不可靠，所以要对它进行重新封装
在Windows平台，is_writable()函数在实际没有文件写权限时也返回真。那是因为，只有文件有只读属性时，操作系统才向PHP报告为假。
在unix中当safe_mode为开启状态下也是不可靠的。
这个函数依靠对文件的先行写入来判断是否真的具有写权限。
3、 类注册器load_class()
这是一个单例模式的函数，如果请求的类没有找到会将它设置为一个静态变量，如果以前存在就直接返回。
4、 is_loaded(); 追踪已经加载的类，这个函数被load_class 调用
5、 get_config(); 加载主配置文件
6、 config_item() 返回指定的配置项
7、 show_error错误处理程序
这个函数调用异常处理类并且使用application/errors/error_general.php模板来显示错误
8、 show_404 404页面处理程序
这个函数和show_error函数相似使用application/errors/error_404.php模板来显示的。
9、 log_message(‘级别’, ‘消息’) 记录错误日志
这个函数可以让你将消息写入记录文件中。你必须在第一个参数中选择三个“级别“中的任何一个, 指明它是那一类消息(调试 debug, 错误 error, 信息info)。 第二个参数是消息本身。
他会调用system/libraries/log.php 进行处理
如果这个config_item('log_threshold') 为0 则不进行任何处理，也就不会记录错误日志了
10、set_status_header 设置http状态头
11、_exception_handler 异常处理程序
12、remove_invisible_characters 去除看不见的字
符 这个函数能防止在ASCII字符之间插入空字符，如Java\0script.
13、html_escape 把一些预定义的字符转换为 HTML 实体
它接受字符串和数组。有助于防止跨站脚本攻击（XSS）。
文件源码：
~~~
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
/**
* CodeIgniter
*
* An open source application development framework for PHP 5.1.6 or newer
*
* @package CodeIgniter
* @author ExpressionEngine Dev Team
* @copyright Copyright (c) 2008 - 2011, EllisLab, Inc.
* @license http://codeigniter.com/user_guide/license.html
* @link http://codeigniter.com
* @since Version 1.0
* @filesource
*/
// ------------------------------------------------------------------------
/**
* Common Functions
*
* Loads the base classes and executes 执行 the request.
*
* @package CodeIgniter
* @subpackage codeigniter
* @category Common Functions
* @author ExpressionEngine Dev Team
* @link http://codeigniter.com/user_guide/
*/
// ------------------------------------------------------------------------
/**
* Determines if the current version of PHP is greater 较大的 then the supplied 提供的 value
*
* Since there are a few 很少的 places where we conditionally 有条件的 test for PHP > 5
* we'll set a static variable.
*
* @access public
* @param string
* @return bool TRUE if the current version is $version or higher
*/
if ( ! function_exists('is_php'))
{
function is_php($version = '5.0.0')
{
static $_is_php;
$version = (string)$version;
if ( ! isset($_is_php[$version]))
{
$_is_php[$version] = (version_compare(PHP_VERSION, $version) < 0) ? FALSE : TRUE;
}
return $_is_php[$version];
}
}
// ------------------------------------------------------------------------
/**
* Tests for file writability 可写性
*
* is_writable() returns TRUE on Windows servers when you really can't write to
* the file, based on the read-only attribute. is_writable() is also unreliable 不可靠的
* on Unix servers if safe_mode is on.
*
* @access private
* @return void
*/
if ( ! function_exists('is_really_writable'))
{
function is_really_writable($file)
{
// If we're on a Unix server with safe_mode off we call is_writable
if (DIRECTORY_SEPARATOR == '/' AND @ini_get("safe_mode") == FALSE)
{
return is_writable($file);
}
// For windows servers and safe_mode "on" installations we'll actually
// write a file then read it. Bah...
if (is_dir($file))
{
$file = rtrim($file, '/').'/'.md5(mt_rand(1,100).mt_rand(1,100));
if (($fp = @fopen($file, FOPEN_WRITE_CREATE)) === FALSE)
{
return FALSE;
}
fclose($fp);
@chmod($file, DIR_WRITE_MODE);
@unlink($file);
return TRUE;
}
elseif ( ! is_file($file) OR ($fp = @fopen($file, FOPEN_WRITE_CREATE)) === FALSE)
{
return FALSE;
}
fclose($fp);
return TRUE;
}
}
// ------------------------------------------------------------------------
/**
* Class registry
*
* This function acts as 扮演一个 a singleton.单例模式 If the requested class does not
* exist it is instantiated and set to a static variable. If it has
* previously 以前 been instantiated the variable is returned.
*
* @access public
* @param string the class name being requested
* @param string the directory where the class should be found
* @param string the class name prefix
* @return object
*/
if ( ! function_exists('load_class'))
{
function &load_class($class, $directory = 'libraries', $prefix = 'CI_')
{
static $_classes = array();
// Does the class exist? If so, we're done...
if (isset($_classes[$class]))
{
return $_classes[$class];
}
$name = FALSE;
// Look for the class first in the local application/libraries folder
// then in the native system/libraries folder
foreach (array(APPPATH, BASEPATH) as $path)
{
if (file_exists($path.$directory.'/'.$class.'.php'))
{
$name = $prefix.$class;
if (class_exists($name) === FALSE)
{
require($path.$directory.'/'.$class.'.php');
}
break;
}
}
// Is the request a class extension? If so we load it too
if (file_exists(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php'))
{
$name = config_item('subclass_prefix').$class;
if (class_exists($name) === FALSE)
{
require(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php');
}
}
// Did we find the class?
if ($name === FALSE)
{
// Note: We use exit() rather then show_error() in order to avoid a
// self-referencing loop with the Excptions class
exit('Unable to locate the specified class: '.$class.'.php');
}
// Keep track of what we just loaded
is_loaded($class);
$_classes[$class] = new $name();
return $_classes[$class];
}
}
// --------------------------------------------------------------------
/**
* Keeps track 追踪 of which libraries have been loaded. This function is
* called by the load_class() function above
*
* @access public
* @return array
*/
if ( ! function_exists('is_loaded'))
{
function &is_loaded($class = '')
{
static $_is_loaded = array();
if ($class != '')
{
$_is_loaded[strtolower($class)] = $class;
}
return $_is_loaded;
}
}
// ------------------------------------------------------------------------
/**
* Loads the main config.php file
*
* This function lets us grab 获取 the config file even 甚至 if the Config class
* hasn't been instantiated yet
*
* @access private
* @return array
*/
if ( ! function_exists('get_config'))
{
function &get_config($replace = array())
{
static $_config;
if (isset($_config))
{
return $_config[0];
}
// Is the config file in the environment folder?
if ( ! defined('ENVIRONMENT') OR ! file_exists($file_path = APPPATH.'config/'.ENVIRONMENT.'/config.php'))
{
$file_path = APPPATH.'config/config.php';
}
// Fetch 取得、拿来 the config file
if ( ! file_exists($file_path))
{
exit('The configuration file does not exist.');
}
require($file_path);
// Does the $config array exist in the file?
if ( ! isset($config) OR ! is_array($config))
{
exit('Your config file does not appear to be formatted correctly.');
}
// Are any values being dynamically replaced?
if (count($replace) > 0)
{
foreach ($replace as $key => $val)
{
if (isset($config[$key]))
{
$config[$key] = $val;
}
}
}
return $_config[0] =& $config;
}
}
// ------------------------------------------------------------------------
/**
* Returns the specified 指定的 config item
*
* @access public
* @return mixed
*/
if ( ! function_exists('config_item'))
{
function config_item($item)
{
static $_config_item = array();
if ( ! isset($_config_item[$item]))
{
$config =& get_config();
if ( ! isset($config[$item]))
{
return FALSE;
}
$_config_item[$item] = $config[$item];
}
return $_config_item[$item];
}
}
// ------------------------------------------------------------------------
/**
* Error Handler 处理器、处理程序
*
* This function lets us invoke 调用 the exception 异常 class and
* display errors using the standard 标准 error template located 地处、处于
* in application/errors/errors.php
* This function will send the error page directly to the
* browser and exit.
*
* @access public
* @return void
*/
if ( ! function_exists('show_error'))
{
function show_error($message, $status_code = 500, $heading = 'An Error Was Encountered')
{
$_error =& load_class('Exceptions', 'core');
echo $_error->show_error($heading, $message, 'error_general', $status_code);
exit;
}
}
// ------------------------------------------------------------------------
/**
* 404 Page Handler
*
* This function is similar 相似的类似的 to the show_error() function above在。。。上面
* However 然而、但是, instead 代替、反而、更换 of the standard 标准、规格、标准版 error
* template it displays
* 404 errors.
*
* @access public
* @return void
*/
if ( ! function_exists('show_404'))
{
function show_404($page = '', $log_error = TRUE)
{
$_error =& load_class('Exceptions', 'core');
$_error->show_404($page, $log_error);
exit;
}
}
// ------------------------------------------------------------------------
/**
* Error Logging Interface 界面
*
* We use this as a simple mechanism 机制、原理 to access 接近、进入、通道 the logging
* class and send messages to be logged.
*
* @access public
* @return void
*/
if ( ! function_exists('log_message'))
{
function log_message($level = 'error', $message, $php_error = FALSE)
{
static $_log;
if (config_item('log_threshold') == 0)
{
return;
}
$_log =& load_class('Log');
$_log->write_log($level, $message, $php_error);
}
}
// ------------------------------------------------------------------------
/**
* Set HTTP Status Header
*
* @access public
* @param int the status code
* @param string
* @return void
*/
if ( ! function_exists('set_status_header'))
{
function set_status_header($code = 200, $text = '')
{
$stati = array(
200 => 'OK',
201 => 'Created',
202 => 'Accepted',
203 => 'Non-Authoritative Information',
204 => 'No Content',
205 => 'Reset Content',
206 => 'Partial Content',
300 => 'Multiple Choices',
301 => 'Moved Permanently',
302 => 'Found',
304 => 'Not Modified',
305 => 'Use Proxy',
307 => 'Temporary Redirect',
400 => 'Bad Request',
401 => 'Unauthorized',
403 => 'Forbidden',
404 => 'Not Found',
405 => 'Method Not Allowed',
406 => 'Not Acceptable',
407 => 'Proxy Authentication Required',
408 => 'Request Timeout',
409 => 'Conflict',
410 => 'Gone',
411 => 'Length Required',
412 => 'Precondition Failed',
413 => 'Request Entity Too Large',
414 => 'Request-URI Too Long',
415 => 'Unsupported Media Type',
416 => 'Requested Range Not Satisfiable',
417 => 'Expectation Failed',
500 => 'Internal Server Error',
501 => 'Not Implemented',
502 => 'Bad Gateway',
503 => 'Service Unavailable',
504 => 'Gateway Timeout',
505 => 'HTTP Version Not Supported'
);
if ($code == '' OR ! is_numeric($code))
{
show_error('Status codes must be numeric', 500);
}
if (isset($stati[$code]) AND $text == '')
{
$text = $stati[$code];
}
if ($text == '')
{
show_error('No status text available. Please check your status code number or supply your own message text.', 500);
}
$server_protocol = (isset($_SERVER['SERVER_PROTOCOL'])) ? $_SERVER['SERVER_PROTOCOL'] : FALSE;
if (substr(php_sapi_name(), 0, 3) == 'cgi')
{
header("Status: {$code} {$text}", TRUE);
}
elseif ($server_protocol == 'HTTP/1.1' OR $server_protocol == 'HTTP/1.0')
{
header($server_protocol." {$code} {$text}", TRUE, $code);
}
else
{
header("HTTP/1.1 {$code} {$text}", TRUE, $code);
}
}
}
// --------------------------------------------------------------------
/**
* Exception Handler
*
* This is the custom 自定义的 exception handler that is declaired at the top
* of Codeigniter.php. The main reason 原因、理由 we use this is to permit 许可
* PHP errors to be logged in our own log files since the user may
* not have access 接近、进入 to server logs. Since this function
* effectively 有效地 intercepts 拦截 PHP errors, however,但是 we also need
* to display errors based on the current error_reporting level.
* We do that with the use of a PHP error template.
*
* @access private
* @return void
*/
if ( ! function_exists('_exception_handler'))
{
function _exception_handler($severity, $message, $filepath, $line)
{
// We don't bother 打扰、麻烦 with "strict" 严格地 notices since they tend 倾向于 to fill up
// the log file with excess information that isn't normally very helpful.
// For example, if you are running PHP 5 and you use version 4 style
// class functions (without prefixes like "public", "private", etc.)
// you'll get notices telling you that these have been deprecated.
if ($severity == E_STRICT)
{
return;
}
$_error =& load_class('Exceptions', 'core');
// Should we display the error? We'll get the current error_reporting
// level and add its bits with the severity bits to find out.
if (($severity & error_reporting()) == $severity)
{
$_error->show_php_error($severity, $message, $filepath, $line);
}
// Should we log the error? No? We're done...
if (config_item('log_threshold') == 0)
{
return;
}
$_error->log_exception($severity, $message, $filepath, $line);
}
}
// --------------------------------------------------------------------
/**
* Remove Invisible 无形的，看不见的 Characters
*
* This prevents sandwiching 夹层 null characters
* between ascii characters, like Java\script.
*
* @access public
* @param string
* @return string
*/
if ( ! function_exists('remove_invisible_characters'))
{
function remove_invisible_characters($str, $url_encoded = TRUE)
{
$non_displayables = array();
// every control character except newline (dec 10)
// carriage return (dec 13), and horizontal tab (dec 09)
if ($url_encoded)
{
$non_displayables[] = '/%0[0-8bcef]/'; // url encoded 00-08, 11, 12, 14, 15
$non_displayables[] = '/%1[0-9a-f]/'; // url encoded 16-31
}
$non_displayables[] = '/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]+/S'; // 00-08, 11, 12, 14-31, 127
do
{
$str = preg_replace($non_displayables, '', $str, -1, $count);
}
while ($count);
return $str;
}
}
// ------------------------------------------------------------------------
/**
* Returns HTML escaped variable
*
* @access public
* @param mixed
* @return mixed
*/
if ( ! function_exists('html_escape'))
{
function html_escape($var)
{
if (is_array($var))
{
return array_map('html_escape', $var);
}
else
{
return htmlspecialchars($var, ENT_QUOTES, config_item('charset'));
}
}
}
/* End of file Common.php */
/* Location: ./system/core/Common.php */
~~~
