【PHP】会话存储方式详解
作者:zhanhailiang 日期:2013-03-15
首先确认会话是否自动开启还是需要通过session_start()来手动开启：
<span class="co0" style="color:rgb(128,128,128); font-style:italic">; 指定会话模块是否在请求开始时自动启动一个会话。默认为 0（不启动）</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; Initialize session on request startup.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.auto-start</span> session.auto_start <span class="sy0" style="color:rgb(102,204,102)">=</span><span class="re2" style="color:rgb(0,0,255)"> 0</span>
在客户端，会话可以存储在cookie或者通过URL参数来获取。依赖于服务器的配置：
<span class="co0" style="color:rgb(128,128,128); font-style:italic">; 指定是否在客户端用 cookie 来存放会话 ID。默认为 1（启用）</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; Whether to use cookies.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.use-cookies</span> session.use_cookies <span class="sy0" style="color:rgb(102,204,102)">=</span><span class="re2" style="color:rgb(0,0,255)"> 1</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; 指定是否在客户端仅仅使用 cookie 来存放会话 ID。。启用此设定可以防止有关通过 URL 传递会话 ID 的攻击。</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; This option forces PHP to fetch and use a cookie for storing and maintaining</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; the session id. We encourage this operation as it's very helpful in combatting</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; session hijacking when not specifying and managing your own session id. It is</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; not the end all be all of session hijacking defense, but it's a good start.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.use-only-cookies</span> session.use_only_cookies <span class="sy0" style="color:rgb(102,204,102)">=</span><span class="re2" style="color:rgb(0,0,255)"> 1</span>
如果确认存储在cookie中，则可以进一点配置会话存储在cookie中的各项配置，如cookie_name，cookie_lifetime，cookie_path，cookie_domain，cookie_secure，cookie_httponly
<span class="co0" style="color:rgb(128,128,128); font-style:italic">; Name of the session (used as cookie name).</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.name</span> session.name <span class="sy0" style="color:rgb(102,204,102)">=</span><span class="re2" style="color:rgb(0,0,255)"> PHPSESSID</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; Lifetime in seconds of cookie or, if 0, until browser is restarted.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.cookie-lifetime</span> session.cookie_lifetime <span class="sy0" style="color:rgb(102,204,102)">=</span><span class="re2" style="color:rgb(0,0,255)"> 0</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; The path for which the cookie is valid.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.cookie-path</span> session.cookie_path <span class="sy0" style="color:rgb(102,204,102)">=</span><span class="re2" style="color:rgb(0,0,255)"> /</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; The domain for which the cookie is valid.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.cookie-domain</span> session.cookie_domain <span class="sy0" style="color:rgb(102,204,102)">=</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; Whether or not to add the httpOnly flag to the cookie, which makes it inaccessible to browser scripting languages such as JavaScript.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.cookie-httponly</span> session.cookie_httponly <span class="sy0" style="color:rgb(102,204,102)">=</span>
在服务器端，同样也可以通过多种方式来存储会话。默认会话存储在文件中，此时session.save_path为创建存储文件的路径。
<span class="co0" style="color:rgb(128,128,128); font-style:italic">; Handler used to store/retrieve data.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.save-handler</span> session.save_handler <span class="sy0" style="color:rgb(102,204,102)">=</span><span class="re2" style="color:rgb(0,0,255)"> files</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; Argument passed to save_handler. In the case of files, this is the path</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; where data files are stored. Note: Windows users have to change this</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; variable in order to use PHP's session functions.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">;</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; The path can be defined as:</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">;</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; session.save_path = "N;/path"</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">;</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; where N is an integer. Instead of storing all the session files in</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; /path, what this will do is use subdirectories N-levels deep, and</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; store the session data in those directories. This is useful if you</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; or your OS have problems with lots of files in one directory, and is</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; a more efficient layout for servers that handle lots of sessions.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">;</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; NOTE 1: PHP will not create this directory structure automatically.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; You can use the script in the ext/session dir for that purpose.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; NOTE 2: See the section on garbage collection below if you choose to</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; use subdirectories for session storage</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">;</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; The file storage module creates files using mode 600 by default.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; You can change that by using</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">;</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; session.save_path = "N;MODE;/path"</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">;</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; where MODE is the octal representation of the mode. Note that this</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; does not overwrite the process's umask.</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">; http://php.net/session.save-path</span> <span class="co0" style="color:rgb(128,128,128); font-style:italic">;session.save_path = "/tmp"</span>
PHP支持通过session_set_save_handler来实现会话处理器的自定义open, close, read, write, destroy, gc处理函数，常见的会话处理器包括使用内存型分配（如mm，memcache等），也可以使用数据库进行存储。由此可见，若需要会话存储与文件系统（例如用数据库PostgreSQL Session Save Handler或默认的文件存储files）协同工作的，此时有可能造成用户定制的会话处理器丢失了未存储数据的会话。若使用内存型分配存储，又需要考虑会话持久化存储问题。
接下来重点讲解memcache(d?)会话处理器。
Memcache模块提供了于memcached方便的面向过程及面向对象的接口，memcached是为了降低动态web应用 从数据库加载数据而产生的一种常驻进程缓存产品。
Memcache模块同时提供了一个session 处理器 (memcache).
更多关于memcached的信息请参见? http://www.memcached.org/.memcached是一个高性能分布式的内存对象缓存系统， 通常被用于降低数据库加载压力以提高动态web应用的响应速度。
此扩展使用了libmemcached库提供的api与memcached服务端进行交互。它同样提供了一个session处理器（memcached）。 它同时提供了一个session处理器（memcached）。
关于libmemcached的更多信息可以在? http://libmemcached.org/libMemcached.html查看。memcache会话处理器配置：
session.save_handler <span class="sy0" style="color:rgb(102,204,102)">=</span><span class="re2" style="color:rgb(0,0,255)"> memcache</span> session.save_path <span class="sy0" style="color:rgb(102,204,102)">=</span> <span class="st0" style="color:rgb(255,0,0)">"tcp://127.0.0.1:11211?persistent=0&weight=1&timeout=1&retry_interval=15,tcp://127.0.0.1:11212?persistent=0&weight=1&timeout=1&retry_interval=15,tcp://127.0.0.1:11213?persistent=0&weight=1&timeout=1&retry_interval=15,tcp://127.0.0.1:11214?persistent=0&weight=1&timeout=1&retry_interval=15"</span>登入後複製数据库处理器可以使用? Session PgSQL来实现（此扩展被认为已无人维护）。也可以使用其它数据库来实现会话存储，只不过需要自定义处理器函数? function.session-set-save-handler.php。具体自定义处理器可参见? maria at junkies dot jp。
