我們開始分析Common.php。
它包含了整個application常用到的一些全域函數。
注意這整份檔案的一個pattern：
它全都會用if ( ! function_exists('xxx'))來確認函數是否被定義過。
原作者群試圖進行防禦性編程。我認為沒必要、這是bad practice。
整個system的製作團隊自己要清楚哪些函數被定義過、又是在哪被定義。用這種防禦性編程是在逃避架構不清的問題。
況且，若是真已被定義過，卻是目的不同的定義，那整個system會crash或是很buggy。
再不然，根本不應該寫成全域函數，而應該以class封裝好，甚至是使用namespace
結果整個system都沒有namespace，這也是我們說CI過時了的一個原因。
這個pattern在helper內也有出現。
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];
}
}
之後某些功能針對不同版本有不同寫法，為了方便比較，建立一個is_php全域函數。
注意此處用了 static 宣告靜態變數。這讓$_is_php陣列內的值能作為暫存，不用每次都去執行運算。
注意這邊有一個函數叫做version_compare。它不過就是字串比較而已。
我想這就是PHP的一個特色：什麼鬼函數都有。
有些人熱愛PHP提供了各種功能；有些人覺得這沒什麼品味。
// ------------------------------------------------------------------------
/**
* Tests for file writability
*
* is_writable() returns TRUE on Windows servers when you really can't write to
* the file, based on the read-only attribute. is_writable() is also unreliable
* on Unix servers if safe_mode is on.
*
* @access private
* @return void
*/
if ( ! function_exists('is_really_writable'))
{
function is_really_writable($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($fp);
return TRUE;
}
}
php內建函數is_writable會根據一個檔案的權限判斷是否可寫入。
不幸的，若是php.ini定義了安全模式，is_writable判斷可寫入的未必真的可寫入。
這邊使用了DIRECTORY_SEPARATOR來判斷作業系統。
在Windows作業系統也有一些屬性要判斷，實作比較複雜：
若是資料夾，就試著在裡面建立一個檔案，建立了卻不能讀取就是不可寫入。
PHP不是包山包海，什麼功能都有提供嗎？怎麼這個深入確認的函數卻是要framework自己提供呀。
// ------------------------------------------------------------------------
/**
* Class registry
*
* This function acts as a singleton. If the requested class does not
* exist it is instantiated and set to a static variable. If it has
* previously been instantiated the variable is returned.
*
* @access public
* @param string the class name being requested
* @param string the directory where the class should be found
* @param string the class name prefix
* @return object
*/
if ( ! function_exists('load_class'))
{
function &load_class($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];
}
}
重頭戲來了，CI利用這個函數將幾乎所有核心類別載入。
也正是因為這個函數，你在其他地方幾乎看不到require或是include函數。
注意函數前面有一個&符號，表示pass by reference。
此處用了static靜態變數來做到儲存，並且會呼叫下面的is_load函數紀錄已經載入的類別。
用全域函數來逐步載入元件，然後紀錄在另一個全域函數的的靜態變數裡面？
我認為這真的超怪異，這應該寫成一個類別吧！
會寫成這樣，我認為是最一開始設計時沒有思考清楚系統該如何抽象化。
注意這邊自訂載入函數的一個重大代價：沒辦法在new一個物件時，傳入任何參數（看看倒數幾行的new相關程式碼）。
也就是PHP程式語言為了支援OOP所提供的類別construtor功能，被全面放棄了！
// --------------------------------------------------------------------
/**
* Keeps track 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 $_is_loaded;
}
}
這就是剛剛所說，利用靜態變數做紀錄的函數。
看到這邊，我個人感覺這像是一大串quick and dirty solution的組合。
繼續往下看，你會發現CI真的用了很多全域函數。
我認為這是procedural programming的一個徵兆：一堆到處用的全域函數。
這也是很多人批評CI一點也不OOP的一個地方。
我個人是覺得獨立function根本不應該有靜態變數。函數還有狀態真的很怪。
// ------------------------------------------------------------------------
/**
* Loads the main config.php file
*
* This function lets us grab the config file even if the Config class
* hasn't been instantiated yet
*
* @access private
* @return array
*/
if ( ! function_exists('get_config'))
{
function &get_config($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'))
{
$file_path = APPPATH.'config/config.php';
}
// Fetch the config file
if ( ! file_exists($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] =& $config;
}
}
// ------------------------------------------------------------------------
/**
* Returns the specified config item
*
* @access public
* @return mixed
*/
if ( ! function_exists('config_item'))
{
function config_item($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
*
* This function lets us invoke the exception class and
* display errors using the standard error template located
* 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', $status_code);
exit;
}
}
用來顯示錯誤訊息的函數。有了它，在任何地方都可以利用show_error來顯示錯誤、debug也很方便。
少數我覺得全域函數幹得好的地方。
注意這個函數跟其他函數有相依性，囧。
// ------------------------------------------------------------------------
/**
* 404 Page Handler
*
* This function is similar to the show_error() function above
* However, instead of the standard error template it displays
* 404 errors.
*
* @access public
* @return void
*/
if ( ! function_exists('show_404'))
{
function show_404($page = '', $log_error = TRUE)
{
$_error =& load_class('Exceptions', 'core');
$_error->show_404($page, $log_error);
exit;
}
}
跟show_error函數差不多。
// ------------------------------------------------------------------------
/**
* Error Logging Interface
*
* We use this as a simple mechanism to access the logging
* class and send messages to be logged.
*
* @access public
* @return void
*/
if ( ! function_exists('log_message'))
{
function log_message($level = 'error', $message, $php_error = FALSE)
{
static $_log;
if (config_item('log_threshold') == 0)
{
return;
}
$_log =& load_class('Log');
$_log->write_log($level, $message, $php_error);
}
}
用來log訊息的函數。
// ------------------------------------------------------------------------
/**
* Set HTTP Status Header
*
* @access public
* @param int the status code
* @param string
* @return void
*/
if ( ! function_exists('set_status_header'))
{
function set_status_header($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, $code);
}
}
}
// --------------------------------------------------------------------
/**
* Exception Handler
*
* This is the custom exception handler that is declaired at the top
* of Codeigniter.php. The main reason we use this is to permit
* PHP errors to be logged in our own log files since the user may
* not have access to server logs. Since this function
* effectively intercepts PHP errors, however, we also need
* to display errors based on the current error_reporting level.
* We do that with the use of a PHP error template.
*
* @access private
* @return void
*/
if ( ! function_exists('_exception_handler'))
{
function _exception_handler($severity, $message, $filepath, $line)
{
// We don't bother with "strict" notices since they tend to fill up
// the log file with excess information that isn't normally very helpful.
// For example, if you are running PHP 5 and you use version 4 style
// class functions (without prefixes like "public", "private", etc.)
// you'll get notices telling you that these have been deprecated.
if ($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, $line);
}
}
// --------------------------------------------------------------------
/**
* Remove Invisible Characters
*
* This prevents sandwiching null characters
* between ascii characters, like Java\0script.
*
* @access public
* @param string
* @return string
*/
if ( ! function_exists('remove_invisible_characters'))
{
function remove_invisible_characters($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 */
用來強化PHP內建htmlspecialchars函數的函數。
可以轉換整個陣列內的字串。
注意到array_map跟htmlspecialchars這兩個內建函數了嗎？PHP內建的函數可是包山包海。