CI框架源码分析之Session类Session.php

CI的Session并不是原生的session，正是我前面所有的cookie based session,另外，CI可以根据用户选择配置是否将session存入数据库中，本人很喜欢这个功能，还有就是“闪出数据”的功能，既闪出数据只是对下次服务器请求可以，之后就会被自动清除。常见使用方法有：
$this->session->set_userdata('some_name', 'some_value'); //设置session数据
$this->session->userdata('item'); //获取session数据
$this->session->unset_userdata('some_name'); //删除session数据
$this->session->sess_destroy(); //销毁session数据
$this->session->set_flashdata('item', 'value'); //设置闪存数据
$this->session->flashdata('item'); //获取闪存数据
$this->session->keep_flashdata('item'); //保留闪存数据

/**
 * CI是 session based cookie
 * 
 * @link http://www.phpddt.com  */
class CI_Session {

	var $sess_encrypt_cookie		= FALSE;  //是否对session加密
	var $sess_use_database			= FALSE; //是否将session存入数据库
	var $sess_table_name			= ''; //session存入数据的表名
	var $sess_expiration			= 7200; //session的过期时间
	var $sess_expire_on_close		= FALSE; //当浏览器窗口关闭时是否自动使session过期
	var $sess_match_ip				= FALSE;//是否通过用户的IP地址来读取 session 的数据
	var $sess_match_useragent		= TRUE; //是否要按照对应的 User Agent 来读取 session 数据。
	var $sess_cookie_name			= 'ci_session'; //cookie名称
	var $cookie_prefix				= ''; //cookie前缀
	var $cookie_path				= ''; //cookie路径
	var $cookie_domain				= ''; //cookie作用域
	var $cookie_secure				= FALSE; //是否在安全的https协议下才有效
	var $sess_time_to_update		= 300; //session cookie多久更新一次
	var $encryption_key				= ''; //加密key
	var $flashdata_key				= 'flash'; 
	var $time_reference				= 'time';
	var $gc_probability				= 5;  //回收session的能力
	var $userdata					= array(); //用户session数据保存变量
	var $CI; //CI超级句柄
	var $now;  //当前时间

	public function __construct($params = array())
	{
		log_message('debug', "Session Class Initialized");

		// 获取CI超级类
		$this->CI =& get_instance();

		// 获取config文件中的配置数据
		foreach (array('sess_encrypt_cookie', 'sess_use_database', 'sess_table_name', 'sess_expiration', 'sess_expire_on_close', 'sess_match_ip', 'sess_match_useragent', 'sess_cookie_name', 'cookie_path', 'cookie_domain', 'cookie_secure', 'sess_time_to_update', 'time_reference', 'cookie_prefix', 'encryption_key') as $key)
		{
			$this->$key = (isset($params[$key])) ? $params[$key] : $this->CI->config->item($key);
		}
                
                //必须设置encryption_key
		if ($this->encryption_key == '')
		{
			show_error('In order to use the Session class you are required to set an encryption key in your config file.');
		}

		// 加载string helper函数
		$this->CI->load->helper('string');

		// D如果对cookie进行加密，则引入加密类
		if ($this->sess_encrypt_cookie == TRUE)
		{
			$this->CI->load->library('encrypt');
		}

		// 如果session计入数据库，则引入db
		if ($this->sess_use_database === TRUE AND $this->sess_table_name != '')
		{
			$this->CI->load->database();
		}

		// 获取当前时间
		$this->now = $this->_get_time();

		// 如果没有设置session的有效时间，默认两年
		if ($this->sess_expiration == 0)
		{
			$this->sess_expiration = (60*60*24*365*2);
		}

		// 获取cookie名称
		$this->sess_cookie_name = $this->cookie_prefix.$this->sess_cookie_name;

		// 如果session不存在，创建新会话
		if ( ! $this->sess_read())
		{
			$this->sess_create();
		}
		else
		{
			$this->sess_update();
		}

		// 闪出标记old的闪出数据
		$this->_flashdata_sweep();

                //将新的闪出数据标记成old 标记成old的数据的数据将会在下次请求时闪出
		$this->_flashdata_mark();

		//回收/删除 过期的session
		$this->_sess_gc();

		log_message('debug', "Session routines successfully run");
	}

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

	/**
	 * 读取session数据
	 */
	function sess_read()
	{
		// 获取session
		$session = $this->CI->input->cookie($this->sess_cookie_name);

		// 没有session  拜拜
		if ($session === FALSE)
		{
			log_message('debug', 'A session cookie was not found.');
			return FALSE;
		}

		// 如果加密了cookie
		if ($this->sess_encrypt_cookie == TRUE)
		{
			$session = $this->CI->encrypt->decode($session);
		}
		else
		{
			// encryption was not used, so we need to check the md5 hash
			$hash	 = substr($session, strlen($session)-32); // get last 32 chars
			$session = substr($session, 0, strlen($session)-32);

			// Does the md5 hash match?  This is to prevent manipulation of session data in userspace
			if ($hash !==  md5($session.$this->encryption_key))
			{
				log_message('error', 'The session cookie data did not match what was expected. This could be a possible hacking attempt.');
				$this->sess_destroy();
				return FALSE;
			}
		}

		// 反序列化存入cookie的session数组
		$session = $this->_unserialize($session);

		// 检测session的数据
		if ( ! is_array($session) OR ! isset($session['session_id']) OR ! isset($session['ip_address']) OR ! isset($session['user_agent']) OR ! isset($session['last_activity']))
		{
			$this->sess_destroy();
			return FALSE;
		}

		// session数据过期了吗
		if (($session['last_activity'] + $this->sess_expiration) < $this->now)
		{
			$this->sess_destroy();
			return FALSE;
		}

		// 是否是根据用户ip来读取session数据
		if ($this->sess_match_ip == TRUE AND $session['ip_address'] != $this->CI->input->ip_address())
		{
			$this->sess_destroy();
			return FALSE;
		}

		// 是否根据ua来匹配session数据
		if ($this->sess_match_useragent == TRUE AND trim($session['user_agent']) != trim(substr($this->CI->input->user_agent(), 0, 120)))
		{
			$this->sess_destroy();
			return FALSE;
		}

		// 如果session入库了，这种方式应该更安全点，当然负载大时，就不建议了，数据库读写压力大
		if ($this->sess_use_database === TRUE)
		{
			$this->CI->db->where('session_id', $session['session_id']);

			if ($this->sess_match_ip == TRUE)
			{
				$this->CI->db->where('ip_address', $session['ip_address']);
			}

			if ($this->sess_match_useragent == TRUE)
			{
				$this->CI->db->where('user_agent', $session['user_agent']);
			}

			$query = $this->CI->db->get($this->sess_table_name);

			// No result?  Kill it!
			if ($query->num_rows() == 0)
			{
				$this->sess_destroy();
				return FALSE;
			}

			// Is there custom data?  If so, add it to the main session array
			$row = $query->row();
			if (isset($row->user_data) AND $row->user_data != '')
			{
				$custom_data = $this->_unserialize($row->user_data);

				if (is_array($custom_data))
				{
					foreach ($custom_data as $key => $val)
					{
						$session[$key] = $val;
					}
				}
			}
		}

		// Session is valid!
		$this->userdata = $session;
		unset($session);

		return TRUE;
	}

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

	/**
	 * 将读取的session数据写入
	 */
	function sess_write()
	{
		// 是否写入db
		if ($this->sess_use_database === FALSE)
		{
			$this->_set_cookie();
			return;
		}

		// set the custom userdata, the session data we will set in a second
		$custom_userdata = $this->userdata;
		$cookie_userdata = array();

		// Before continuing, we need to determine if there is any custom data to deal with.
		// Let's determine this by removing the default indexes to see if there's anything left in the array
		// and set the session data while we're at it
		foreach (array('session_id','ip_address','user_agent','last_activity') as $val)
		{
			unset($custom_userdata[$val]);
			$cookie_userdata[$val] = $this->userdata[$val];
		}

		// Did we find any custom data?  If not, we turn the empty array into a string
		// since there's no reason to serialize and store an empty array in the DB
		if (count($custom_userdata) === 0)
		{
			$custom_userdata = '';
		}
		else
		{
			// Serialize the custom data array so we can store it
			$custom_userdata = $this->_serialize($custom_userdata);
		}

		// 更新session记录
		$this->CI->db->where('session_id', $this->userdata['session_id']);
		$this->CI->db->update($this->sess_table_name, array('last_activity' => $this->userdata['last_activity'], 'user_data' => $custom_userdata));

		// Write the cookie.  Notice that we manually pass the cookie data array to the
		// _set_cookie() function. Normally that function will store $this->userdata, but
		// in this case that array contains custom data, which we do not want in the cookie.
		$this->_set_cookie($cookie_userdata);
	}

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

	/**
	 * 创建一个新的session
	 */
	function sess_create()
	{
                //保证sessid 安全唯一
		$sessid = '';
		while (strlen($sessid) < 32)
		{
			$sessid .= mt_rand(0, mt_getrandmax());
		}
		$sessid .= $this->CI->input->ip_address();

		$this->userdata = array(
							'session_id'	=> md5(uniqid($sessid, TRUE)),
							'ip_address'	=> $this->CI->input->ip_address(),
							'user_agent'	=> substr($this->CI->input->user_agent(), 0, 120),
							'last_activity'	=> $this->now,
							'user_data'		=> ''
							);


		// Save the data to the DB if needed
		if ($this->sess_use_database === TRUE)
		{
			$this->CI->db->query($this->CI->db->insert_string($this->sess_table_name, $this->userdata));
		}

		// Write the cookie
		$this->_set_cookie();
	}

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

	/**
	 * 更新session
	 */
	function sess_update()
	{
		// 默认五分钟更新
		if (($this->userdata['last_activity'] + $this->sess_time_to_update) >= $this->now)
		{
			return;
		}

		// Save the old session id so we know which record to
		// update in the database if we need it
		$old_sessid = $this->userdata['session_id'];
		$new_sessid = '';
		while (strlen($new_sessid) < 32)
		{
			$new_sessid .= mt_rand(0, mt_getrandmax());
		}

		// To make the session ID even more secure we'll combine it with the user's IP
		$new_sessid .= $this->CI->input->ip_address();

		// Turn it into a hash
		$new_sessid = md5(uniqid($new_sessid, TRUE));

		// Update the session data in the session data array
		$this->userdata['session_id'] = $new_sessid;
		$this->userdata['last_activity'] = $this->now;

		// _set_cookie() will handle this for us if we aren't using database sessions
		// by pushing all userdata to the cookie.
		$cookie_data = NULL;

		// 更新数据库中几率
		if ($this->sess_use_database === TRUE)
		{
			// set cookie explicitly to only have our session data
			$cookie_data = array();
			foreach (array('session_id','ip_address','user_agent','last_activity') as $val)
			{
				$cookie_data[$val] = $this->userdata[$val];
			}

			$this->CI->db->query($this->CI->db->update_string($this->sess_table_name, array('last_activity' => $this->now, 'session_id' => $new_sessid), array('session_id' => $old_sessid)));
		}

		// 重新写入session
		$this->_set_cookie($cookie_data);
	}

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

	/**
	 *销毁当前所有session数据
	 */
	function sess_destroy()
	{
		// Kill the session DB row
		if ($this->sess_use_database === TRUE && isset($this->userdata['session_id']))
		{
			$this->CI->db->where('session_id', $this->userdata['session_id']);
			$this->CI->db->delete($this->sess_table_name);
		}

		// Kill the cookie
		setcookie(
					$this->sess_cookie_name,
					addslashes(serialize(array())),
					($this->now - 31500000),
					$this->cookie_path,
					$this->cookie_domain,
					0
				);

		// Kill session data
		$this->userdata = array();
	}

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

	/**
	 * 获取session数组指定元素的值
	 */
	function userdata($item)
	{
		return ( ! isset($this->userdata[$item])) ? FALSE : $this->userdata[$item];
	}

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

	/**
	 * 获取所有session数据
	 */
	function all_userdata()
	{
		return $this->userdata;
	}

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

	/**
	 * 添加和修改自定义的session数据
	 */
	function set_userdata($newdata = array(), $newval = '')
	{
		if (is_string($newdata))
		{
			$newdata = array($newdata => $newval);
		}
                //支持数组组合方式
		if (count($newdata) > 0)
		{
			foreach ($newdata as $key => $val)
			{
				$this->userdata[$key] = $val;
			}
		}

		$this->sess_write();
	}

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

	/**
	 * 删除session数组中的元素，
	 */
	function unset_userdata($newdata = array())
	{
		if (is_string($newdata))
		{
			$newdata = array($newdata => '');
		}

		if (count($newdata) > 0)
		{
			foreach ($newdata as $key => $val)
			{
				unset($this->userdata[$key]);
			}
		}

		$this->sess_write();
	}

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

	/**
	 * Add or change flashdata, only available
	 * until the next request
	 *
	 * @access	public
	 * @param	mixed
	 * @param	string
	 * @return	void
	 */
	function set_flashdata($newdata = array(), $newval = '')
	{
		if (is_string($newdata))
		{
			$newdata = array($newdata => $newval);
		}

		if (count($newdata) > 0)
		{
			foreach ($newdata as $key => $val)
			{
				$flashdata_key = $this->flashdata_key.':new:'.$key;
				$this->set_userdata($flashdata_key, $val);
			}
		}
	}

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

	/**
	 * CI支持闪出数据也就是说 Session数据只对下次服务器请求可用,有时候如果你还想在下个请求后的请求还有效。。。
         * keep_flashdata功能就是讲持续保持闪出数据，使其在下个请求也有效
	 */
	function keep_flashdata($key)
	{

                //将闪出数据标记成new
		$old_flashdata_key = $this->flashdata_key.':old:'.$key;
		$value = $this->userdata($old_flashdata_key);

		$new_flashdata_key = $this->flashdata_key.':new:'.$key;
		$this->set_userdata($new_flashdata_key, $value);
	}

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

	/**
	 * 获取闪出数据
	 */
	function flashdata($key)
	{
		$flashdata_key = $this->flashdata_key.':old:'.$key;
		return $this->userdata($flashdata_key);
	}

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

	/**
	 * 将闪出数据标记成old，以便_flashdata_sweep清除数据
	 */
	function _flashdata_mark()
	{
		$userdata = $this->all_userdata();
		foreach ($userdata as $name => $value)
		{
			$parts = explode(':new:', $name);
			if (is_array($parts) && count($parts) === 2)
			{
				$new_name = $this->flashdata_key.':old:'.$parts[1];
				$this->set_userdata($new_name, $value);
				$this->unset_userdata($name);
			}
		}
	}

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

	/**
	 * 将标记成old的闪出数据闪出
	 */

	function _flashdata_sweep()
	{
		$userdata = $this->all_userdata();
		foreach ($userdata as $key => $value)
		{
			if (strpos($key, ':old:'))
			{
				$this->unset_userdata($key);
			}
		}

	}

	//获取当前时间
	function _get_time()
	{
		if (strtolower($this->time_reference) == 'gmt')
		{
			$now = time();
			$time = mktime(gmdate("H", $now), gmdate("i", $now), gmdate("s", $now), gmdate("m", $now), gmdate("d", $now), gmdate("Y", $now));
		}
		else
		{
			$time = time();
		}

		return $time;
	}

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

	/**
	 * 写入session cookie
	 *
	 */
	function _set_cookie($cookie_data = NULL)
	{
		if (is_null($cookie_data))
		{
			$cookie_data = $this->userdata;
		}

		// 序列化数组
		$cookie_data = $this->_serialize($cookie_data);
                
                //加密数据
		if ($this->sess_encrypt_cookie == TRUE)
		{
			$cookie_data = $this->CI->encrypt->encode($cookie_data);
		}
		else
		{
			// if encryption is not used, we provide an md5 hash to prevent userside tampering
			$cookie_data = $cookie_data.md5($cookie_data.$this->encryption_key);
		}
                
                //sess_expire_on_close为TRUE则，浏览器关闭，session失效
		$expire = ($this->sess_expire_on_close === TRUE) ? 0 : $this->sess_expiration + time();

		// Set the cookie
		setcookie(
					$this->sess_cookie_name,
					$cookie_data,
					$expire,
					$this->cookie_path,
					$this->cookie_domain,
					$this->cookie_secure
				);
	}

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

	/**
	 * 序列化数组
	 */
	function _serialize($data)
	{
		if (is_array($data))
		{
			foreach ($data as $key => $val)
			{
				if (is_string($val))
				{
					$data[$key] = str_replace('\\', '{{slash}}', $val);
				}
			}
		}
		else
		{
			if (is_string($data))
			{
				$data = str_replace('\\', '{{slash}}', $data);
			}
		}

		return serialize($data);
	}

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

	/**
	 * 反序列化数组
	 */
	function _unserialize($data)
	{
		$data = @unserialize(strip_slashes($data));

		if (is_array($data))
		{
			foreach ($data as $key => $val)
			{
				if (is_string($val))
				{
					$data[$key] = str_replace('{{slash}}', '\\', $val);
				}
			}

			return $data;
		}

		return (is_string($data)) ? str_replace('{{slash}}', '\\', $data) : $data;
	}

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

	/**
	 * 回收/删除数据库中失效的session信息
	 */
	function _sess_gc()
	{
		if ($this->sess_use_database != TRUE)
		{
			return;
		}

		srand(time());
		if ((rand() % 100) < $this->gc_probability)
		{
			$expire = $this->now - $this->sess_expiration;

			$this->CI->db->where("last_activity < {$expire}");
			$this->CI->db->delete($this->sess_table_name);

			log_message('debug', 'Session garbage collection performed.');
		}
	}
}