CodeIgniter.php 引入的第一个文件,定义了很多贯穿整个框架的函数。


知识点

引用

Common.php

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/**
* CodeIgniter
*
* An open source application development framework for PHP
*
* This content is released under the MIT License (MIT)
*
* Copyright (c) 2014 - 2015, British Columbia Institute of Technology
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
* @package CodeIgniter
* @author EllisLab Dev Team
* @copyright Copyright (c) 2008 - 2014, EllisLab, Inc. (http://ellislab.com/)
* @copyright Copyright (c) 2014 - 2015, British Columbia Institute of Technology (http://bcit.ca/)
* @license http://opensource.org/licenses/MIT MIT License
* @link http://codeigniter.com
* @since Version 1.0.0
* @filesource
*/
defined('BASEPATH') OR exit('No direct script access allowed');

/**
* Common Functions
*
* Loads the base classes and executes the request.
*
* @package CodeIgniter
* @subpackage CodeIgniter
* @category Common Functions
* @author EllisLab Dev Team
* @link http://codeigniter.com/user_guide/
*/

// ------------------------------------------------------------------------

if ( ! function_exists('is_php'))
{
/**
* Determines if the current version of PHP is equal to or greater than the supplied value
*
* @param string
* @return bool TRUE if the current version is $version or higher
*/
function is_php($version)
{
static $_is_php;
$version = (string) $version;

if ( ! isset($_is_php[$version]))
{
$_is_php[$version] = version_compare(PHP_VERSION, $version, '>=');
}

return $_is_php[$version];
}
}

功能:判断当前版本是否大于$version

mixed version_compare ( string $version1 , string $version2 [, string $operator ] ) 默认情况下,在第一个版本低于第二个时,version_compare() 返回 -1;如果两者相等,返回 0;第二个版本更低时则返回 1。
当使用了可选参数 operator 时,如果关系是操作符所指定的那个,函数将返回 TRUE,否则返回 FALSE。

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// ------------------------------------------------------------------------

if ( ! function_exists('is_really_writable'))
{
/**
* Tests for file writability
*
* 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
* on Unix servers if safe_mode is on.
*
* @link https://bugs.php.net/bug.php?id=54709
* @param string
* @return bool
*/
function is_really_writable($file)
{
// If we're on a Unix server with safe_mode off we call is_writable
if (DIRECTORY_SEPARATOR === '/' && (is_php('5.4') OR ! ini_get('safe_mode')))
{
return is_writable($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());
if (($fp = @fopen($file, 'ab')) === FALSE)
{
return FALSE;
}

fclose($fp);
@chmod($file, 0777);
@unlink($file);
return TRUE;
}
elseif ( ! is_file($file) OR ($fp = @fopen($file, 'ab')) === FALSE)
{
return FALSE;
}

fclose($fp);
return TRUE;
}
}

功能:判断当前文件(或文件夹)是否真正可写。

用到的函数:fopen、@(抑制错误的显示)、unlink()(删除文件)、chmod()(修改文件权限)
小技巧:$file = rtrim($file, '/').'/'.md5(mt_rand());

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    // ------------------------------------------------------------------------

if ( ! function_exists('load_class'))
{
/**
* Class registry
*
* This function acts as a singleton. If the requested class does not
* exist it is instantiated and set to a static variable. If it has
* previously been instantiated the variable is returned.
*
* @param string the class name being requested
* @param string the directory where the class should be found
* @param string an optional argument to pass to the class constructor
* @return object
*/
function &load_class($class, $directory = 'libraries', $param = NULL)
{
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
// 导入“CI”开头的系统类(优先导入自定义的类)
foreach (array(APPPATH, BASEPATH) as $path)
{
if (file_exists($path.$directory.'/'.$class.'.php'))
{
$name = 'CI_'.$class;

if (class_exists($name, FALSE) === FALSE)
{
require_once($path.$directory.'/'.$class.'.php');
}

break;
}
}

// Is the request a class extension? If so we load it too
//是否需要导入扩展
if (file_exists(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php'))
{
$name = config_item('subclass_prefix').$class;

if (class_exists($name, FALSE) === FALSE)
{
require_once(APPPATH.$directory.'/'.$name.'.php');
}
}

// Did we find the class?
if ($name === FALSE)
{
// Note: We use exit() rather than show_error() in order to avoid a
// self-referencing loop with the Exceptions class
set_status_header(503);
echo 'Unable to locate the specified class: '.$class.'.php';
exit(5); // EXIT_UNK_CLASS
}

// Keep track of what we just loaded
//保存已经载入的类
is_loaded($class);

$_classes[$class] = isset($param)
? new $name($param)
: new $name();
return $_classes[$class];
}
}

>功能:导入指定类。

>函数:`bool class_exists ( string $class_name [, bool $autoload = true ] )` :检测类是否存在,类名大小写不敏感。

// --------------------------------------------------------------------

if ( ! function_exists('is_loaded'))
{
/**
* Keeps track of which libraries have been loaded. This function is
* called by the load_class() function above
*
* @param string
* @return array
*/
function &is_loaded($class = '')
{
static $_is_loaded = array();

if ($class !== '')
{
$_is_loaded[strtolower($class)] = $class;
}

return $_is_loaded;
}
}

// ------------------------------------------------------------------------

if ( ! function_exists('get_config'))
{
/**
* Loads the main config.php file
*
* This function lets us grab the config file even if the Config class
* hasn't been instantiated yet
*
* @param array
* @return array
*/
function &get_config(Array $replace = array())
{
//定义静态数组存储配置
static $config;

if (empty($config))
{
$file_path = APPPATH.'config/config.php';
$found = FALSE;
if (file_exists($file_path))
{
$found = TRUE;
require($file_path);
}

// Is the config file in the environment folder?
if (file_exists($file_path = APPPATH.'config/'.ENVIRONMENT.'/config.php'))
{
require($file_path);
}
elseif ( ! $found)
{
set_status_header(503);
echo 'The configuration file does not exist.';
exit(3); // EXIT_CONFIG
}

// Does the $config array exist in the file?
if ( ! isset($config) OR ! is_array($config))
{
set_status_header(503);
echo 'Your config file does not appear to be formatted correctly.';
exit(3); // EXIT_CONFIG
}
}

// Are any values being dynamically added or replaced?
foreach ($replace as $key => $val)
{
$config[$key] = $val;
}

return $config;
}
}

读取 config/config.php文件

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// ------------------------------------------------------------------------

if ( ! function_exists('config_item'))
{
/**
* Returns the specified config item
*
* @param string
* @return mixed
*/
function config_item($item)
{
static $_config;

if (empty($_config))
{
// references cannot be directly assigned to static variables, so we use an array
$_config[0] =& get_config();
}

return isset($_config[0][$item]) ? $_config[0][$item] : NULL;
}
}

获取指定配置。

技巧:别名不能拿直接赋值给静态变量,这里用到了数组

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// ------------------------------------------------------------------------

if ( ! function_exists('get_mimes'))
{
/**
* Returns the MIME types array from config/mimes.php
*
* @return array
*/
function &get_mimes()
{
static $_mimes;

if (empty($_mimes))
{
if (file_exists(APPPATH.'config/'.ENVIRONMENT.'/mimes.php'))
{
$_mimes = include(APPPATH.'config/'.ENVIRONMENT.'/mimes.php');
}
elseif (file_exists(APPPATH.'config/mimes.php'))
{
$_mimes = include(APPPATH.'config/mimes.php');
}
else
{
$_mimes = array();
}
}

return $_mimes;
}
}

MIME (Multipurpose Internet Mail Extensions) 是描述消息内容类型的因特网标准。

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// ------------------------------------------------------------------------

if ( ! function_exists('is_https'))
{
/**
* Is HTTPS?
*
* Determines if the application is accessed via an encrypted
* (HTTPS) connection.
*
* @return bool
*/
function is_https()
{
if ( ! empty($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) !== 'off')
{
return TRUE;
}
elseif (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] === 'https')
{
return TRUE;
}
elseif ( ! empty($_SERVER['HTTP_FRONT_END_HTTPS']) && strtolower($_SERVER['HTTP_FRONT_END_HTTPS']) !== 'off')
{
return TRUE;
}

return FALSE;
}
}

// ------------------------------------------------------------------------

if ( ! function_exists('is_cli'))
{

/**
* Is CLI?
*
* Test to see if a request was made from the command line.
*
* @return bool
*/
function is_cli()
{
return (PHP_SAPI === 'cli' OR defined('STDIN'));
}
}

// ------------------------------------------------------------------------

if ( ! function_exists('show_error'))
{
/**
* Error Handler
*
* This function lets us invoke the exception class and
* display errors using the standard error template located
* in application/views/errors/error_general.php
* This function will send the error page directly to the
* browser and exit.
*
* @param string
* @param int
* @param string
* @return void
*/
function show_error($message, $status_code = 500, $heading = 'An Error Was Encountered')
{
$status_code = abs($status_code);
if ($status_code < 100)
{
$exit_status = $status_code + 9; // 9 is EXIT__AUTO_MIN
if ($exit_status > 125) // 125 is EXIT__AUTO_MAX
{
$exit_status = 1; // EXIT_ERROR
}

$status_code = 500;
}
else
{
$exit_status = 1; // EXIT_ERROR
}

$_error =& load_class('Exceptions', 'core');
echo $_error->show_error($heading, $message, 'error_general', $status_code);
exit($exit_status);
}
}

功能:报错(通过Exceptions类显示错误界面)
函数:abs() :取绝对值

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// ------------------------------------------------------------------------

if ( ! function_exists('show_404'))
{
/**
* 404 Page Handler
*
* This function is similar to the show_error() function above
* However, instead of the standard error template it displays
* 404 errors.
*
* @param string
* @param bool
* @return void
*/
function show_404($page = '', $log_error = TRUE)
{
$_error =& load_class('Exceptions', 'core');
$_error->show_404($page, $log_error);
exit(4); // EXIT_UNKNOWN_FILE
}
}

// ------------------------------------------------------------------------

if ( ! function_exists('log_message'))
{
/**
* Error Logging Interface
*
* We use this as a simple mechanism to access the logging
* class and send messages to be logged.
*
* @param string the error level: 'error', 'debug' or 'info'
* @param string the error message
* @return void
*/
function log_message($level, $message)
{
static $_log;

if ($_log === NULL)
{
// references cannot be directly assigned to static variables, so we use an array
$_log[0] =& load_class('Log', 'core');
}

$_log[0]->write_log($level, $message);
}
}

// ------------------------------------------------------------------------

if ( ! function_exists('set_status_header'))
{
/**
* Set HTTP Status Header
*
* @param int the status code
* @param string
* @return void
*/
function set_status_header($code = 200, $text = '')
{
if (is_cli())
{
return;
}

if (empty($code) OR ! is_numeric($code))
{
show_error('Status codes must be numeric', 500);
}

if (empty($text))
{
is_int($code) OR $code = (int) $code;
$stati = array(
100 => 'Continue',
101 => 'Switching Protocols',

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',
303 => 'See Other',
304 => 'Not Modified',
305 => 'Use Proxy',
307 => 'Temporary Redirect',

400 => 'Bad Request',
401 => 'Unauthorized',
402 => 'Payment Required',
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',
422 => 'Unprocessable Entity',

500 => 'Internal Server Error',
501 => 'Not Implemented',
502 => 'Bad Gateway',
503 => 'Service Unavailable',
504 => 'Gateway Timeout',
505 => 'HTTP Version Not Supported'
);

if (isset($stati[$code]))
{
$text = $stati[$code];
}
else
{
show_error('No status text available. Please check your status code number or supply your own message text.', 500);
}
}

//以cgi类型和以服务器模块形式类型的不同发出响应的方式。
if (strpos(PHP_SAPI, 'cgi') === 0)
{
header('Status: '.$code.' '.$text, TRUE);
}
else
{
$server_protocol = isset($_SERVER['SERVER_PROTOCOL']) ? $_SERVER['SERVER_PROTOCOL'] : 'HTTP/1.1';
header($server_protocol.' '.$code.' '.$text, TRUE, $code);
}
}
}

// --------------------------------------------------------------------

if ( ! function_exists('_error_handler'))
{
/**
* Error Handler
*
* This is the custom error handler that is declared at the (relative)
* top of CodeIgniter.php. The main reason we use this is to permit
* PHP errors to be logged in our own log files since the user may
* not have access to server logs. Since this function effectively
* intercepts PHP errors, however, we also need to display errors
* based on the current error_reporting level.
* We do that with the use of a PHP error template.
*
* @param int $severity
* @param string $message
* @param string $filepath
* @param int $line
* @return void
*/
function _error_handler($severity, $message, $filepath, $line)
{
$is_error = (((E_ERROR | E_COMPILE_ERROR | E_CORE_ERROR | E_USER_ERROR) & $severity) === $severity);

// When an error occurred, set the status header to '500 Internal Server Error'
// to indicate to the client something went wrong.
// This can't be done within the $_error->show_php_error method because
// it is only called when the display_errors flag is set (which isn't usually
// the case in a production environment) or when errors are ignored because
// they are above the error_reporting threshold.
if ($is_error)
{
set_status_header(500);
}

// Should we ignore 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)
{
return;
}

$_error =& load_class('Exceptions', 'core');
$_error->log_exception($severity, $message, $filepath, $line);

// Should we display the error?
if (str_ireplace(array('off', 'none', 'no', 'false', 'null'), '', ini_get('display_errors')))
{
$_error->show_php_error($severity, $message, $filepath, $line);
}

// If the error is fatal, the execution of the script should be stopped because
// errors can't be recovered from. Halting the script conforms with PHP's
// default error handling. See http://www.php.net/manual/en/errorfunc.constants.php
if ($is_error)
{
exit(1); // EXIT_ERROR
}
}
}

功能:(引入 Exception)处理异常
函数:str_ireplace — str_replace() 的忽略大小写版本

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// ------------------------------------------------------------------------

if ( ! function_exists('_exception_handler'))
{
/**
* Exception Handler
*
* Sends uncaught exceptions to the logger and displays them
* only if display_errors is On so that they don't show up in
* production environments.
*
* @param Exception $exception
* @return void
*/
function _exception_handler($exception)
{
$_error =& load_class('Exceptions', 'core');
$_error->log_exception('error', 'Exception: '.$exception->getMessage(), $exception->getFile(), $exception->getLine());

// Should we display the error?
if (str_ireplace(array('off', 'none', 'no', 'false', 'null'), '', ini_get('display_errors')))
{
$_error->show_exception($exception);
}

exit(1); // EXIT_ERROR
}
}

// ------------------------------------------------------------------------

if ( ! function_exists('_shutdown_handler'))
{
/**
* Shutdown Handler
*
* This is the shutdown handler that is declared at the top
* of CodeIgniter.php. The main reason we use this is to simulate
* a complete custom exception handler.
*
* E_STRICT is purposively neglected because such events may have
* been caught. Duplication or none? None is preferred for now.
*
* @link http://insomanic.me.uk/post/229851073/php-trick-catching-fatal-errors-e-error-with-a
* @return void
*/
function _shutdown_handler()
{
$last_error = error_get_last();
if (isset($last_error) &&
($last_error['type'] & (E_ERROR | E_PARSE | E_CORE_ERROR | E_CORE_WARNING | E_COMPILE_ERROR | E_COMPILE_WARNING)))
{
_error_handler($last_error['type'], $last_error['message'], $last_error['file'], $last_error['line']);
}
}
}

// --------------------------------------------------------------------

if ( ! function_exists('remove_invisible_characters'))
{
/**
* Remove Invisible Characters
*
* This prevents sandwiching null characters
* between ascii characters, like Java\0script.
*
* @param string
* @param bool
* @return string
*/
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;
}
}

// ------------------------------------------------------------------------

if ( ! function_exists('html_escape'))
{
/**
* Returns HTML escaped variable.
*
* @param mixed $var The input string or array of strings to be escaped.
* @param bool $double_encode $double_encode set to FALSE prevents escaping twice.
* @return mixed The escaped string or array of strings as a result.
*/
function html_escape($var, $double_encode = TRUE)
{
if (empty($var))
{
return $var;
}

if (is_array($var))
{
return array_map('html_escape', $var, array_fill(0, count($var), $double_encode));
}

return htmlspecialchars($var, ENT_QUOTES, config_item('charset'), $double_encode);
}
}

功能:返回转义字符
函数:array array_map ( callable $callback , array $arr1 [, array $... ] )array_map() 返回一个数组,该数组包含了 arr1 中的所有单元经过 callback 作用过之后的单元。callback 接受的参数数目应该和传递给 array_map() 函数的数组数目一致。

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// ------------------------------------------------------------------------

if ( ! function_exists('_stringify_attributes'))
{
/**
* Stringify attributes for use in HTML tags.
*
* Helper function used to convert a string, array, or object
* of attributes to a string.
*
* @param mixed string, array, object
* @param bool
* @return string
*/
function _stringify_attributes($attributes, $js = FALSE)
{
$atts = NULL;

if (empty($attributes))
{
return $atts;
}

if (is_string($attributes))
{
return ' '.$attributes;
}

$attributes = (array) $attributes;

foreach ($attributes as $key => $val)
{
$atts .= ($js) ? $key.'='.$val.',' : ' '.$key.'="'.$val.'"';
}

return rtrim($atts, ',');
}
}

功能:anything 2 stirng
函数:is_string()

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// ------------------------------------------------------------------------

if ( ! function_exists('function_usable'))
{
/**
* Function usable
*
* Executes a function_exists() check, and if the Suhosin PHP
* extension is loaded - checks whether the function that is
* checked might be disabled in there as well.
*
* This is useful as function_exists() will return FALSE for
* functions disabled via the *disable_functions* php.ini
* setting, but not for *suhosin.executor.func.blacklist* and
* *suhosin.executor.disable_eval*. These settings will just
* terminate script execution if a disabled function is executed.
*
* The above described behavior turned out to be a bug in Suhosin,
* but even though a fix was commited for 0.9.34 on 2012-02-12,
* that version is yet to be released. This function will therefore
* be just temporary, but would probably be kept for a few years.
*
* @link http://www.hardened-php.net/suhosin/
* @param string $function_name Function to check for
* @return bool TRUE if the function exists and is safe to call,
* FALSE otherwise.
*/
function function_usable($function_name)
{
static $_suhosin_func_blacklist;

if (function_exists($function_name))
{
if ( ! isset($_suhosin_func_blacklist))
{
$_suhosin_func_blacklist = extension_loaded('suhosin')
? explode(',', trim(ini_get('suhosin.executor.func.blacklist')))
: array();
}

return ! in_array($function_name, $_suhosin_func_blacklist, TRUE);
}

return FALSE;
}
}