CodeIgniter 核心代码阅读-公用函数文件Common.php

Common.php公用函数文件

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

//判断正在使用的PHP的版本号是否高于你所提供的 version_number 
//如果已安装的PHP版本号等于或高于你所提供的版本号，本函数将返回布尔值 TRUE。如果安装的PHP版本号低于你所提供的那个版本号，本函数将返回 FALSE。
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];
	}
}

//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。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。 通常情况下，只有在这个信息不可靠的平台上才推荐使用。
//此函数也可用于判断文件夹是否有可写权限
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;
	}
}


//实例化类，实例化的类都是单类，保存在$_classes中，返回的是对$_classes中的类的引用
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];
	}
}

//标记已加载类，这个理解起来比较别扭，不是判断是否已加载某个类，而是标记所有已加载的类
//返回的是对静态变量$_is_loaded的引用
if ( ! function_exists('is_loaded'))
{
	function &is_loaded($class = '')
	{
		static $_is_loaded = array();

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

		return $_is_loaded;
	}
}

//获取配置数组
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;
	}
}

//获取配置项
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];
	}
}

//显示错误

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;
	}
}

//显示404错误
if ( ! function_exists('show_404'))
{
	function show_404($page = '', $log_error = TRUE)
	{
		$_error =& load_class('Exceptions', 'core');
		$_error->show_404($page, $log_error);
		exit;
	}
}

//记录错误日志
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);
	}
}

//设置HTTP状态
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);
		}
	}
}

//记录异常日志
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);
	}
}

//这个函数能防止在ASCII字符之间插入空字符，如Java\0script.
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;
	}
}

//利用此功能可以方便的使用htmlspecialchars()函数。它接受字符串和数组。有助于防止跨站脚本攻击（XSS）。
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'));
		}
	}
}