怎樣通過SessionIdInterface 來改變默認的會話存儲機制？

M66 2025-07-04

PHP 的會話管理是Web 開發中非常重要的一部分，它為開發者提供了存儲和管理用戶會話數據的能力。默認情況下，PHP 使用文件存儲會話數據，但是在某些情況下，開發者可能希望將會話數據存儲在其他地方，比如數據庫、緩存系統等。為了實現這種自定義存儲機制，PHP 提供了SessionIdInterface接口，讓我們能夠靈活地控制會話存儲的方式。

1. 理解SessionIdInterface

SessionIdInterface是PHP 7.4 版本引入的接口，旨在提供一種方式，使開發者能夠定制會話的ID 生成與存儲機制。通常情況下，PHP 會話的ID 是由PHP 內部自動生成並保存在$_SESSION中，而通過實現SessionIdInterface ，開發者可以自定義會話ID 的獲取與保存方式。

具體來說， SessionIdInterface提供了兩個主要方法：

getSessionId() : 用於獲取當前會話的ID。
setSessionId(string $id) : 用於設置會話的ID。

通過實現這兩個方法，開發者可以控制會話ID 如何生成、如何保存，以及如何從存儲中讀取。

2. 通過SessionIdInterface 改變會話存儲機制

要改變默認的會話存儲機制，我們需要實現一個自定義的Session Handler 類，該類會實現SessionHandlerInterface ，並結合SessionIdInterface來提供一個新的存儲方式。以下是一個簡單的示例，展示如何使用數據庫來存儲會話數據：

步驟1：創建自定義Session Handler

首先，我們需要創建一個類，來實現SessionHandlerInterface和SessionIdInterface 。這個類將用於處理會話數據的存儲和獲取。

 <span><span><span class="hljs-class"><span class="hljs-keyword">class</span></span></span><span> </span><span><span class="hljs-title">DatabaseSessionHandler</span></span><span> </span><span><span class="hljs-keyword">implements</span></span><span> </span><span><span class="hljs-title">SessionHandlerInterface</span></span><span>, </span><span><span class="hljs-title">SessionIdInterface</span></span><span>
{
    </span><span><span class="hljs-keyword">private</span></span><span> </span><span><span class="hljs-variable">$db</span></span><span>;

    </span><span><span class="hljs-keyword">public</span></span><span> </span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">__construct</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$dbConnection</span></span></span><span>)
    {
        </span><span><span class="hljs-variable language_">$this</span></span><span>-&gt;db = </span><span><span class="hljs-variable">$dbConnection</span></span><span>;
    }

    </span><span><span class="hljs-keyword">public</span></span><span> </span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">open</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$savePath</span></span></span><span>, </span><span><span class="hljs-variable">$sessionName</span></span><span>)
    {
        </span><span><span class="hljs-comment">// 這裡可以進行數據庫連接檢查等操作</span></span><span>
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-literal">true</span></span><span>;
    }

    </span><span><span class="hljs-keyword">public</span></span><span> </span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">close</span></span><span>(</span><span><span class="hljs-params"></span></span><span>)
    {
        </span><span><span class="hljs-comment">// 關閉數據庫連接</span></span><span>
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-literal">true</span></span><span>;
    }

    </span><span><span class="hljs-keyword">public</span></span><span> </span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">read</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$sessionId</span></span></span><span>)
    {
        </span><span><span class="hljs-comment">// 從數據庫讀取會話數據</span></span><span>
        </span><span><span class="hljs-variable">$query</span></span><span> = </span><span><span class="hljs-string">"SELECT session_data FROM sessions WHERE session_id = :session_id"</span></span><span>;
        </span><span><span class="hljs-variable">$stmt</span></span><span> = </span><span><span class="hljs-variable language_">$this</span></span><span>-&gt;db-&gt;</span><span><span class="hljs-title function_ invoke__">prepare</span></span><span>(</span><span><span class="hljs-variable">$query</span></span><span>);
        </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">bindParam</span></span><span>(</span><span><span class="hljs-string">':session_id'</span></span><span>, </span><span><span class="hljs-variable">$sessionId</span></span><span>);
        </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">execute</span></span><span>();
        
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">fetchColumn</span></span><span>();
    }

    </span><span><span class="hljs-keyword">public</span></span><span> </span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">write</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$sessionId</span></span></span><span>, </span><span><span class="hljs-variable">$sessionData</span></span><span>)
    {
        </span><span><span class="hljs-comment">// 將會話數據寫入數據庫</span></span><span>
        </span><span><span class="hljs-variable">$query</span></span><span> = </span><span><span class="hljs-string">"REPLACE INTO sessions (session_id, session_data) VALUES (:session_id, :session_data)"</span></span><span>;
        </span><span><span class="hljs-variable">$stmt</span></span><span> = </span><span><span class="hljs-variable language_">$this</span></span><span>-&gt;db-&gt;</span><span><span class="hljs-title function_ invoke__">prepare</span></span><span>(</span><span><span class="hljs-variable">$query</span></span><span>);
        </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">bindParam</span></span><span>(</span><span><span class="hljs-string">':session_id'</span></span><span>, </span><span><span class="hljs-variable">$sessionId</span></span><span>);
        </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">bindParam</span></span><span>(</span><span><span class="hljs-string">':session_data'</span></span><span>, </span><span><span class="hljs-variable">$sessionData</span></span><span>);
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">execute</span></span><span>();
    }

    </span><span><span class="hljs-keyword">public</span></span><span> </span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">destroy</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$sessionId</span></span></span><span>)
    {
        </span><span><span class="hljs-comment">// 刪除數據庫中的會話數據</span></span><span>
        </span><span><span class="hljs-variable">$query</span></span><span> = </span><span><span class="hljs-string">"DELETE FROM sessions WHERE session_id = :session_id"</span></span><span>;
        </span><span><span class="hljs-variable">$stmt</span></span><span> = </span><span><span class="hljs-variable language_">$this</span></span><span>-&gt;db-&gt;</span><span><span class="hljs-title function_ invoke__">prepare</span></span><span>(</span><span><span class="hljs-variable">$query</span></span><span>);
        </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">bindParam</span></span><span>(</span><span><span class="hljs-string">':session_id'</span></span><span>, </span><span><span class="hljs-variable">$sessionId</span></span><span>);
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">execute</span></span><span>();
    }

    </span><span><span class="hljs-keyword">public</span></span><span> </span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">gc</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$maxlifetime</span></span></span><span>)
    {
        </span><span><span class="hljs-comment">// 清理過期的會話</span></span><span>
        </span><span><span class="hljs-variable">$query</span></span><span> = </span><span><span class="hljs-string">"DELETE FROM sessions WHERE last_access &lt; :maxlifetime"</span></span><span>;
        </span><span><span class="hljs-variable">$stmt</span></span><span> = </span><span><span class="hljs-variable language_">$this</span></span><span>-&gt;db-&gt;</span><span><span class="hljs-title function_ invoke__">prepare</span></span><span>(</span><span><span class="hljs-variable">$query</span></span><span>);
        </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">bindParam</span></span><span>(</span><span><span class="hljs-string">':maxlifetime'</span></span><span>, </span><span><span class="hljs-variable">$maxlifetime</span></span><span>);
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$stmt</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">execute</span></span><span>();
    }

    </span><span><span class="hljs-comment">// 實現 SessionIdInterface 接口方法</span></span><span>
    </span><span><span class="hljs-keyword">public</span></span><span> </span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">getSessionId</span></span><span>(</span><span><span class="hljs-params"></span></span><span>)
    {
        </span><span><span class="hljs-comment">// 自定義獲取 Session ID 方式</span></span><span>
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-title function_ invoke__">session_id</span></span><span>();  </span><span><span class="hljs-comment">// 或者自定義邏輯生成 ID</span></span><span>
    }

    </span><span><span class="hljs-keyword">public</span></span><span> </span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">setSessionId</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$id</span></span></span><span>)
    {
        </span><span><span class="hljs-comment">// 自定義設置 Session ID 方式</span></span><span>
        </span><span><span class="hljs-title function_ invoke__">session_id</span></span><span>(</span><span><span class="hljs-variable">$id</span></span><span>);  </span><span><span class="hljs-comment">// 或者自定義邏輯保存 ID</span></span><span>
    }
}
</span></span>

步驟2：註冊自定義Session Handler

在PHP 中，我們需要通過session_set_save_handler()函數來註冊自定義的會話處理器。這樣PHP 就會使用我們的自定義類來處理會話的存儲和讀取。

 <span><span><span class="hljs-comment">// 假設 $dbConnection 是一個有效的 PDO 數據庫連接對象</span></span><span>
</span><span><span class="hljs-variable">$handler</span></span><span> = </span><span><span class="hljs-keyword">new</span></span><span> </span><span><span class="hljs-title class_">DatabaseSessionHandler</span></span><span>(</span><span><span class="hljs-variable">$dbConnection</span></span><span>);

</span><span><span class="hljs-comment">// 註冊自定義會話處理器</span></span><span>
</span><span><span class="hljs-title function_ invoke__">session_set_save_handler</span></span><span>(
    [</span><span><span class="hljs-variable">$handler</span></span><span>, </span><span><span class="hljs-string">'open'</span></span><span>],
    [</span><span><span class="hljs-variable">$handler</span></span><span>, </span><span><span class="hljs-string">'close'</span></span><span>],
    [</span><span><span class="hljs-variable">$handler</span></span><span>, </span><span><span class="hljs-string">'read'</span></span><span>],
    [</span><span><span class="hljs-variable">$handler</span></span><span>, </span><span><span class="hljs-string">'write'</span></span><span>],
    [</span><span><span class="hljs-variable">$handler</span></span><span>, </span><span><span class="hljs-string">'destroy'</span></span><span>],
    [</span><span><span class="hljs-variable">$handler</span></span><span>, </span><span><span class="hljs-string">'gc'</span></span><span>]
);

</span><span><span class="hljs-comment">// 啟動會話</span></span><span>
</span><span><span class="hljs-title function_ invoke__">session_start</span></span><span>();
</span></span>

步驟3：啟動會話並使用

現在，PHP 會話數據就會被存儲在數據庫中，而不是默認的文件系統中。你可以像通常一樣使用$_SESSION變量來存取會話數據：

 <span><span><span class="hljs-comment">// 設置會話數據</span></span><span>
</span><span><span class="hljs-variable">$_SESSION</span></span><span>[</span><span><span class="hljs-string">'user'</span></span><span>] = </span><span><span class="hljs-string">'John Doe'</span></span><span>;

</span><span><span class="hljs-comment">// 獲取會話數據</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$_SESSION</span></span><span>[</span><span><span class="hljs-string">'user'</span></span><span>];  </span><span><span class="hljs-comment">// 輸出 John Doe</span></span><span>
</span></span>

3. 總結

通過實現SessionIdInterface和SessionHandlerInterface接口，開發者可以靈活地自定義PHP 的會話存儲機制，不再依賴於文件系統或PHP 默認的存儲方式。無論是存儲在數據庫中，還是緩存系統中，都會話管理都能更加高效、靈活。同時，這也提高了系統的可擴展性，能夠適應不同的應用場景。

通過自定義會話存儲方式，你不僅能夠控制會話數據存儲的位置，還能對會話ID 的生成、存儲和讀取方式進行更精細的控制，從而滿足更複雜的業務需求。