一、Session類的參數：可以在application/config/config.php 文件中找到以下的 Session 相關的參數:
| 參數 | 默認 | 選項 | 描述 |
|---|---|---|---|
| sess_cookie_name | ci_session | 無 | 你想要保存 Session Cookie 的名字。 |
| sess_expiration | 7200 | 無 | session 持續的秒數。默認是2個小時(7200秒)。如果將這個數值設爲: 0，就可以得到 永久 session。 |
| sess_expire_on_close | FALSE | TRUE/FALSE (boolean) | 這個選項決定當瀏覽器窗口關閉時是否自動使session過期。 |
| sess_encrypt_cookie | FALSE | TRUE/FALSE (布爾值boolean) | 是否對 session 數據加密. |
| sess_use_database | FALSE | TRUE/FALSE (布爾值boolean) | 是否將 session 數據存放入數據庫中。在開啓這個選項前，你要先創建一個數據庫表。 |
| sess_table_name | ci_sessions | 任何有效的 SQL 表名 | session 數據庫表的名字。 |
| sess_time_to_update | 300 | 時間以秒計算 | 這個選項控制 session 類多久會產生一個新的session 和 session id。 |
| sess_match_ip | FALSE | TRUE/FALSE (布爾值boolean) | 是否通過用戶的IP地址來讀取 session 的數據。 注意 ，有些網絡運行商 ISPs 會動態的改變IP, 所以將這個選項設爲 FALSE， 纔有可能得到永久的 session。 |
| sess_match_useragent | TRUE | TRUE/FALSE (布爾值boolean) | 是否要按照對應的 User Agent 來讀取 session 數據。 |
二、Session類的構造函數：構造函數做的事情有：
①初始化Session參數
②判斷加密密鑰是否爲空，則返回錯誤
③加載字符串輔助函數使用strip_slashes()函數
④判斷是否加密Session，如果加密Session則加載加密類
⑤判斷Session是否寫入數據庫，則加載數據庫類
⑥初始化當前時間
⑦初始化過期時間
⑧初始化$this->sess_cookie_name
⑨判斷Session是否存在，如不存在創建Session，若存在更新Session
⑩垃圾回收
public function __construct($params = array())
{
log_message('debug', "Session Class Initialized");
// Set the super object to a local variable for use throughout the class
$this->CI =& get_instance();
// Set all the session preferences, which can either be set
// manually via the $params array above or via the config file
// 設置session參數，首先判斷是否設置$params，如果沒有則從config文件中設置
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);
}
// 判斷加密密鑰是否爲空，爲空則返回錯誤
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.');
}
// Load the string helper so we can use the strip_slashes() function
// 加載字符串輔助函數以使用strip_slashes()函數
$this->CI->load->helper('string');
// Do we need encryption? If so, load the encryption class
// 判斷是否加密Session,如果加密session則加載類庫encrypt
if ($this->sess_encrypt_cookie == TRUE)
{
$this->CI->load->library('encrypt');
}
// Are we using a database? If so, load it
// 判斷是否將Session存入數據庫，如果存入則加載數據庫類
if ($this->sess_use_database === TRUE AND $this->sess_table_name != '')
{
$this->CI->load->database();
}
// Set the "now" time. Can either be GMT or server time, based on the
// config prefs. We use this to set the "last activity" time
// 獲取當前時間
$this->now = $this->_get_time();
// Set the session length. If the session expiration is
// set to zero we'll set the expiration two years from now.
// 如果sess_expiration設置爲0，則把過期時間設置爲兩年後
if ($this->sess_expiration == 0)
{
$this->sess_expiration = (60*60*24*365*2);
}
// Set the cookie name
// 設置Session名稱，爲$this->cookie_prefix.$this->sess_cookie_name，$this->cookie_prefix在config文件中設置
$this->sess_cookie_name = $this->cookie_prefix.$this->sess_cookie_name;
// Run the Session routine. If a session doesn't exist we'll
// create a new one. If it does, we'll update it.
// 如果Session不存在，則創建Session，否則更新它
if ( ! $this->sess_read())
{
$this->sess_create();
}
else
{
$this->sess_update();
}
// Delete 'old' flashdata (from last request)
$this->_flashdata_sweep();
// Mark all new flashdata as old (data will be deleted before next request)
$this->_flashdata_mark();
// Delete expired sessions if necessary
$this->_sess_gc();
log_message('debug', "Session routines successfully run");
}三、構造函數中調用的sess_read()方法：獲取當前的Session
function sess_read()
{
// Fetch the cookie
// 獲取cookie的值
$session = $this->CI->input->cookie($this->sess_cookie_name);
// No cookie? Goodbye cruel world!...
// 如果沒有cookie，返回錯誤
if ($session === FALSE)
{
log_message('debug', 'A session cookie was not found.');
return FALSE;
}
// Decrypt the cookie data
// 判斷是否加密session，如果爲真則加密session
if ($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;
}
}
// Unserialize the session array
$session = $this->_unserialize($session);
// Is the session data we unserialized an array with the correct format?
// 判斷被unserialized的數組是否有正確的session格式，若沒有執行sess_destroy
if ( ! is_array($session) OR ! isset($session['session_id']) OR ! isset($session['ip_address']) OR ! isset($session['user_agent']) OR ! isset($session['last_activity']))
{
$this->sess_destroy();
return FALSE;
}
// Is the session current?
// 判斷最新的一個活躍時間戳+Session有效期是否小於現在時間，若小於sess_destroy
if (($session['last_activity'] + $this->sess_expiration) < $this->now)
{
$this->sess_destroy();
return FALSE;
}
// Does the IP Match?
// 判斷IP是否匹配
if ($this->sess_match_ip == TRUE AND $session['ip_address'] != $this->CI->input->ip_address())
{
$this->sess_destroy();
return FALSE;
}
// Does the User Agent Match?
// 判斷user_agent是否匹配
if ($this->sess_match_useragent == TRUE AND trim($session['user_agent']) != trim(substr($this->CI->input->user_agent(), 0, 120)))
{
$this->sess_destroy();
return FALSE;
}
// Is there a corresponding session in the DB?
// 判斷數據庫中的Session是否正確
if ($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;
}四：創建Session的方法sess_create()
function sess_create()
{
// 初始化sessid，並將它用mt_rand(0, mt_getrandmax())循環生成隨機值，直到sessid的長度大於32
$sessid = '';
while (strlen($sessid) < 32)
{
$sessid .= mt_rand(0, mt_getrandmax());
}
// To make the session ID even more secure we'll combine it with the user's IP
// 爲了更安全，將IP地址結合，加到$sessid的末尾
$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' => $this->now,
'user_data' => ''
);
// Save the data to the DB if needed
// 如果啓用了Session存入數據庫，則將數據存入數據庫中
if ($this->sess_use_database === TRUE)
{
$this->CI->db->query($this->CI->db->insert_string($this->sess_table_name, $this->userdata));
}
// Write the cookie
// 設置cookie
$this->_set_cookie();
}該方法調用私有成員方法_set_cookie()
function _set_cookie($cookie_data = NULL)
{
if (is_null($cookie_data))
{
$cookie_data = $this->userdata;
}
// Serialize the userdata for the cookie
// 序列化userdata
$cookie_data = $this->_serialize($cookie_data);
// 判斷是否加密Session
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
// 如果加密沒有啓用，則提供一個md5 hash
$cookie_data = $cookie_data.md5($cookie_data.$this->encryption_key);
}
$expire = ($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,
$this->cookie_secure
);
}五、Session更新方法sess_update()
function sess_update()
{
// We only update the session every five minutes by default
// 默認每五分鐘更新一次Session
if (($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
// 記住舊的Session id所以我們能從數據庫中知道哪個記錄要更新
$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.
$cookie_data = NULL;
// Update the session ID and last_activity field in the DB if needed
// 如果是Session保存在數據庫，則更新相應的記錄
if ($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)));
}
// Write the cookie
$this->_set_cookie($cookie_data);
}六、Session銷燬方法sess_destroy()
function sess_destroy()
{
// Kill the session DB row
// 如果Session是存在數據庫中，則刪除數據庫中的指定行
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
// 將過期時間設置爲一個過去的時間
setcookie(
$this->sess_cookie_name,
addslashes(serialize(array())),
($this->now - 31500000),
$this->cookie_path,
$this->cookie_domain,
0
);
// Kill session data
// 將$this->userdata設定爲空數組
$this->userdata = array();
}
function set_userdata($newdata = array(), $newval = '')
{
// 如果$newdata是字符串，則說明是隻添加一個用戶數據
if (is_string($newdata))
{
$newdata = array($newdata => $newval);
}
// 添加一個數組
if (count($newdata) > 0)
{
foreach ($newdata as $key => $val)
{
$this->userdata[$key] = $val;
}
}
$this->sess_write();
}該方法調用成員方法sess_write()
function sess_write()
{
// Are we saving custom data to the DB? If not, all we do is update the cookie
// 如果不是將Sessin存入數據庫，只要更新當前cookie就行了
if ($this->sess_use_database === FALSE)
{
$this->_set_cookie();
return;
}
// set the custom userdata, the session data we will set in a second
// 自定義的Session數據
$custom_userdata = $this->userdata;
$cookie_userdata = array();
// Before continuing, we need to determine if there is any custom data to deal with.
// Let's determine this by removing the default indexes to see if there's anything left in the array
// and set the session data while we're at it
// 將$custom_userdata中不是用戶自定義數據的銷燬
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
// 如果沒有自定義Session數據，我們將空數組轉換爲空字符串
if (count($custom_userdata) === 0)
{
$custom_userdata = '';
}
else
{
// Serialize the custom data array so we can store it
// 如果設置了自定義Session數據，則將其序列化
$custom_userdata = $this->_serialize($custom_userdata);
}
// Run the update query
// 更新數據庫中的last_activity和user_data
$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.
// 設置不是自定義Session數據
$this->_set_cookie($cookie_userdata);
}八、垃圾回收方法_sess_gc()
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.');
}
}