CI源码分析-Common.php


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

    /**
     * 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。

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

    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());

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

    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

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

    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

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

    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。

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

    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

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

    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

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

    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。

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

    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()

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

    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;
        }
    }

文章作者: Fengit
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