文件位于system/core/common.php，是框架核心文件。
该文件中定义了一系列的函数，都是框架运行中经常需要用到的。下面逐一介绍。
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];
}
}
该函数用于进行php版本比较，如果运行的php版本大于等于输入的php版本参数，则返回true。这里建立了一个$is_php静态数组，把新版本参数比较的结果存在数组里，如果再有类似的版本参数传入，不用比较，直接返回结果。是一种空间换时间的做法。
is_really_writable
/**
* Tests for file writability
*
* is_writable() returns TRUE on Windows servers when you really can't write to
* the file, based on the read-only attribute. is_writable() is also unreliable
* on Unix servers if safe_mode is on.
*
* @link https://bugs.php.net/bug.php?id=54709
* @param string
* @return bool
*/
function is_really_writable($file)
{
// If we're on a Unix server with safe_mode off we call is_writable
//用DIRECTORY_SEPARATOR === '/'来判断是unix系统，
if (DIRECTORY_SEPARATOR === '/' && (is_php('5.4') OR ! ini_get('safe_mode')))
{
return is_writable($file);
} /* For Windows servers and safe_mode "on" installations we'll actually
* write a file then read it. Bah...
* 对于windows操作系统和安全模式的处理方法
*/
if (is_dir($file))//对于目录
{
$file = rtrim($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)//对于文件
{
return FALSE;
} fclose($fp);
return TRUE;
}
该函数用于判断文件或目录是否可写。
对于linux系统未使用安全模式的情况，直接调用php函数is_writable($file)即可。
对于windows系统和使用安全模式的linux系统则根据是文件夹还是文件采取不同的方式：文件夹是 在看是否可在里面新建一个可读写的文件；文件是看是否可读写打开。
&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 mixed 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
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
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: '.$class.'.php';
exit(5); // EXIT_UNK_CLASS
} // Keep track of what we just loaded
is_loaded($class); $_classes[$class] = isset($param)
? new $name($param)
: new $name();
return $_classes[$class];
}
}
该函数用于类的注册，核心函数。
这个函数维护一个单例模式，即如果请求注册的类$class已经被实例化过了，则把保存的实例化对象返回，如果没有实例化过，就实例化该类。这个做法避免新建大量的对象，减少内存消耗，也减少了框架使用对象的维护成本，避免使用的混乱。
在搜索类文件的时候，既会搜索系统的类文件，也会搜索用户自定义的类文件。用户自定义类名需要定义统一的前缀，这个前缀在application/config/config.php文件的subclass_prefix变量中定义。
该函数前面有一个&，表明是引用传递返回值。即返回的对象以后发生变化的时候，在这个函数中定义的$_classes[$class]也会发生变化。参考知乎上的解释。
&is_loaded($class = '')
/**
* 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;
}
该函数可以获取已经在load_class函数中注册的类名数组，也可以往 类名数组中添加一个已经注册的类名。使用引用传递返回值。
&get_config(Array $replace = array())
/**
* 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())
{
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 $config;
}
}
该函数用来加载application/config/config.php中的$config数组变量。当然，如果存在，也加载用户根据环境定义的config.php文件。
config.php文件中定义了一些系统和应用程序的设置，包括使用何种编码，是否采用csrf,自定义的类的类名前缀等等。
同时，使用该函数通过$replace也可以追加一些设置。
该函数使用静态局部变量数组$config来存储。使用引用传递返回值。
config_item($item)
/**
* Returns the specified config item
*
* @param string
* @return mixed
*/
function config_item($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;
}
该函数用于获取某一个具体的在get_config()中定义的$config数组的值。
&get_mimes()
/**
* Returns the MIME types array from config/mimes.php
*
* @return array
*/
function &get_mimes()
{
static $_mimes; if (empty($_mimes))
{
$_mimes = file_exists(APPPATH.'config/mimes.php')
? include(APPPATH.'config/mimes.php')
: array(); if (file_exists(APPPATH.'config/'.ENVIRONMENT.'/mimes.php'))
{
$_mimes = array_merge($_mimes, include(APPPATH.'config/'.ENVIRONMENT.'/mimes.php'));
}
} return $_mimes;
}
该函数用于获取在application/config/mimes.php中定义的mime类型数组。主要用于文件上传时候的检测。
is_https()
/**
* Is HTTPS?
*
* Determines if the application is accessed via an encrypted
* (HTTPS) connection.
*
* @return bool
*/
function is_https()
{
if ( ! empty($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) !== 'off')
{
return TRUE;
}
elseif (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && strtolower($_SERVER['HTTP_X_FORWARDED_PROTO']) === 'https')
{
return TRUE;
}
elseif ( ! empty($_SERVER['HTTP_FRONT_END_HTTPS']) && strtolower($_SERVER['HTTP_FRONT_END_HTTPS']) !== 'off')
{
return TRUE;
} return FALSE;
}
该函数判断请求是否是http请求。
is_cli()
/**
* Is CLI?
*
* Test to see if a request was made from the command line.
*
* @return bool
*/
function is_cli()
{
return (PHP_SAPI === 'cli' OR defined('STDIN'));
}
该函数用于判断请求是否是命令行方式。
show_error($message, $status_code = 500, $heading = 'An Error Was Encountered')
/**
* Error Handler
*
* This function lets us invoke the exception class and
* display errors using the standard error template located
* in application/views/errors/error_general.php
* This function will send the error page directly to the
* browser and exit.
*
* @param string
* @param int
* @param string
* @return void
*/
function show_error($message, $status_code = 500, $heading = 'An Error Was Encountered')
{
$status_code = abs($status_code);//取绝对值
if ($status_code < 100)
{
$exit_status = $status_code + 9; // 9 is EXIT__AUTO_MIN
$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);
}
该函数用于主动显示一个错误提示给用户，无论是命令行模式还是浏览器显示。调用的是Exceptions类的show_error方法。
show_404($page = '', $log_error = TRUE)
/**
* 404 Page Handler
*
* This function is similar to the show_error() function above
* However, instead of the standard error template it displays
* 404 errors.
*
* @param string
* @param bool
* @return void
*/
function show_404($page = '', $log_error = TRUE)
{
$_error =& load_class('Exceptions', 'core');
$_error->show_404($page, $log_error);
exit(4); // EXIT_UNKNOWN_FILE
}
该函数用于主动显示一个404错误给用户，无论是命令行模式还是浏览器显示。调用的是Exceptions类的show_404方法。
log_message($level, $message)
/**
* Error Logging Interface
*
* We use this as a simple mechanism to access the logging
* class and send messages to be logged.
*
* @param string the error level: 'error', 'debug' or 'info'
* @param string the error message
* @return void
*/
function log_message($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, $message);
}
该函数用于记录日志。常用的函数。日志分Error，Debug，Info三个级别。调用的是Log类的write_log方法。
set_status_header($code = 200, $text = '')
/**
* Set HTTP Status Header
*
* @param int the status code
* @param string
* @return void
*/
function set_status_header($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;
$stati = array(
100 => 'Continue',
101 => 'Switching Protocols', 200 => 'OK',
201 => 'Created',
202 => 'Accepted',
203 => 'Non-Authoritative Information',
204 => 'No Content',
205 => 'Reset Content',
206 => 'Partial Content', 300 => 'Multiple Choices',
301 => 'Moved Permanently',
302 => 'Found',
303 => 'See Other',
304 => 'Not Modified',
305 => 'Use Proxy',
307 => 'Temporary Redirect', 400 => 'Bad Request',
401 => 'Unauthorized',
402 => 'Payment Required',
403 => 'Forbidden',
404 => 'Not Found',
405 => 'Method Not Allowed',
406 => 'Not Acceptable',
407 => 'Proxy Authentication Required',
408 => 'Request Timeout',
409 => 'Conflict',
410 => 'Gone',
411 => 'Length Required',
412 => 'Precondition Failed',
413 => 'Request Entity Too Large',
414 => 'Request-URI Too Long',
415 => 'Unsupported Media Type',
416 => 'Requested Range Not Satisfiable',
417 => 'Expectation Failed',
422 => 'Unprocessable Entity',
426 => 'Upgrade Required',
428 => 'Precondition Required',
429 => 'Too Many Requests',
431 => 'Request Header Fields Too Large', 500 => 'Internal Server Error',
501 => 'Not Implemented',
502 => 'Bad Gateway',
503 => 'Service Unavailable',
504 => 'Gateway Timeout',
505 => 'HTTP Version Not Supported',
511 => 'Network Authentication Required',
); if (isset($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);
}
} if (strpos(PHP_SAPI, 'cgi') === 0)
{
header('Status: '.$code.' '.$text, TRUE);
return;
} $server_protocol = (isset($_SERVER['SERVER_PROTOCOL']) && in_array($_SERVER['SERVER_PROTOCOL'], array('HTTP/1.0', 'HTTP/1.1', 'HTTP/2'), TRUE))
? $_SERVER['SERVER_PROTOCOL'] : 'HTTP/1.1';
header($server_protocol.' '.$code.' '.$text, TRUE, $code);
}
手动设置返回的http头，如果设置的是“500”。那么浏览器解析的Status Code就是500。
_error_handler($severity, $message, $filepath, $line)
/**
* 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_PARSE | 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
}
}
该函数是在CodeIgniter.php中使用set_error_handler设置的用户自定义错误处理函数。该函数用于处理脚本中出现的错误。值得说明的是，以下级别的错误不能由用户定义的函数来处理： E_ERROR、 E_PARSE、 E_CORE_ERROR、 E_CORE_WARNING、 E_COMPILE_ERROR、 E_COMPILE_WARNING。所以即使不小心进入了这个方法，也需要屏蔽掉。
对于在函数前加了@屏蔽warning的函数，也会进入这个方法。但是它的error_reporting()返回值是0，而不管系统设置的是什么。可以由此来判断直接返回，不做处理。
$severity包含了错误的级别，是一个 integer。
调用Exceptions类的show_php_error方法。
_exception_handler($exception)
/**
* 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()); is_cli() OR set_status_header(500);
// 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
}
该函数是在CodeIgniter.php中使用set_exception_handler设置的用户自定义异常处理函数。该函数是记录异常到日志中，并且展示给用户看到该异常。
set_error_handler和set_exception_handler的不同参见网上资料。
_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'], $last_error['line']);
}
}
该函数是在CodeIgniter.php中使用register_shutdown_function 注册的会在php中止时执行的函数。
remove_invisible_characters($str, $url_encoded = TRUE)
/**
* Remove Invisible Characters
*
* This prevents sandwiching null characters
* between ascii characters, like Java\0script.
*
* @param string
* @param bool
* @return string
*/
function remove_invisible_characters($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]/i'; // url encoded 00-08, 11, 12, 14, 15
$non_displayables[] = '/%1[0-9a-f]/i'; // url encoded 16-31
$non_displayables[] = '/%7f/i'; // url encoded 127
} $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;
}
该函数用于清除字符串中的不可见字符。 $non_displayables[] = '/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]+/S'; 会匹配ascII中00-08, 11, 12, 14-31, 127的字符，这些字符都是不可见的。参见ascII字符表。
html_escape($var, $double_encode = TRUE)
/**
* 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))
{
foreach (array_keys($var) as $key)
{
$var[$key] = html_escape($var[$key], $double_encode);
} return $var;
} return htmlspecialchars($var, ENT_QUOTES, config_item('charset'), $double_encode);
}
该函数用于将字符串或者字符串数组转换为html实体。
_stringify_attributes($attributes, $js = FALSE)
/**
* Stringify attributes for use in HTML tags.
*
* Helper function used to convert a string, array, or object
* of attributes to a string.
*
* @param mixed string, array, object
* @param bool
* @return string
*/
function _stringify_attributes($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($atts, ',');
}
将一个字符串属性，数组属性或者对象属性转换为一个字符串。主要用于在显示html页面的时候使用。
function_usable($function_name)
/**
* 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 committed 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;
}
函数功能类似于function_exist(),不过在外面包装了一层，还需要检查下函数是否在suhosin.executor.func.blacklist中（类似于黑名单？），如果在还是会返回false。