怎麼用socket_select 檢查多個Socket 是否可讀？ PHP 實用技巧講解

gitbox 2025-09-12

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 本文件為教學用途，展示如何在 PHP 中使用 socket_select 檢查多個 Socket 是否可讀。</span></span><span>
</span><span><span class="hljs-comment">// 請確保已啟用 sockets 擴展。</span></span><span>

</span><span><span class="hljs-comment">// 建立示例 sockets（伺服器 socket 和幾個客戶端 socket），省略創建過程以聚焦核心邏輯。</span></span><span>

</span><span><span class="hljs-comment">// -------------------------------</span></span><span>

</span><span><span class="hljs-meta">?&gt;</span></span><span>

</span><span><span class="hljs-comment"># 怎麼用 socket_select 檢查多個 Socket 是否可讀？PHP 實用技巧講解</span></span><span>

在開發基於網絡通信的 PHP 應用時，我們常常需要同時處理多個連接，尤其是在構建聊天室、游戏伺服器或即时通信系统等场景中。這時，`</span><span><span class="hljs-title function_ invoke__">socket_select</span></span><span>()` 函數就顯得尤為重要。它允許你在多個 socket 之間進行非阻塞的可讀寫檢查，極大提高了效率。

本文將帶你深入了解如何使用 `socket_select` 檢查多個 socket 是否可讀，並給出一個簡潔實用的示例。

</span><span><span class="hljs-comment">## 什麼是 socket_select？</span></span><span>

`</span><span><span class="hljs-title function_ invoke__">socket_select</span></span><span>()` 是 PHP 對底層 `</span><span><span class="hljs-title function_ invoke__">select</span></span><span>()` 系統調用的封裝。它用於檢測一組 sockets 是否可以進行讀、寫或異常操作，並且可以設定超時。

```php
</span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-title function_ invoke__">socket_select</span></span><span>(</span><span><span class="hljs-keyword">array</span></span><span> &amp;</span><span><span class="hljs-variable">$read</span></span><span>, </span><span><span class="hljs-keyword">array</span></span><span> &amp;</span><span><span class="hljs-variable">$write</span></span><span>, </span><span><span class="hljs-keyword">array</span></span><span> &amp;</span><span><span class="hljs-variable">$except</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$tv_sec</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$tv_usec</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>)
</span></span>

$read ：你想監控是否可讀的sockets。
$write ：你想監控是否可寫的sockets（可傳null）。
$except ：你想監控是否有異常的sockets（可傳null）。
$tv_sec和$tv_usec ：分別是秒和微秒級的超時時間。

實戰示例：檢查多個socket 是否有數據可讀

以下是一個實際使用socket_select的PHP 代碼片段，它檢查多個客戶端socket 是否有數據到達：

 <span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 创建主伺服器 socket</span></span><span>
</span><span><span class="hljs-variable">$server</span></span><span> = </span><span><span class="hljs-title function_ invoke__">socket_create</span></span><span>(AF_INET, SOCK_STREAM, SOL_TCP);
</span><span><span class="hljs-title function_ invoke__">socket_bind</span></span><span>(</span><span><span class="hljs-variable">$server</span></span><span>, </span><span><span class="hljs-string">'127.0.0.1'</span></span><span>, </span><span><span class="hljs-number">8888</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">socket_listen</span></span><span>(</span><span><span class="hljs-variable">$server</span></span><span>);

</span><span><span class="hljs-comment">// 設置非阻塞</span></span><span>
</span><span><span class="hljs-title function_ invoke__">socket_set_nonblock</span></span><span>(</span><span><span class="hljs-variable">$server</span></span><span>);

</span><span><span class="hljs-variable">$clients</span></span><span> = [</span><span><span class="hljs-variable">$server</span></span><span>];

</span><span><span class="hljs-keyword">while</span></span><span> (</span><span><span class="hljs-literal">true</span></span><span>) {
    </span><span><span class="hljs-variable">$readSockets</span></span><span> = </span><span><span class="hljs-variable">$clients</span></span><span>;
    </span><span><span class="hljs-variable">$writeSockets</span></span><span> = </span><span><span class="hljs-literal">null</span></span><span>;
    </span><span><span class="hljs-variable">$exceptSockets</span></span><span> = </span><span><span class="hljs-literal">null</span></span><span>;

    </span><span><span class="hljs-comment">// 檢查哪些 socket 可讀（不阻塞，1 秒超時）</span></span><span>
    </span><span><span class="hljs-variable">$numChangedSockets</span></span><span> = </span><span><span class="hljs-title function_ invoke__">socket_select</span></span><span>(</span><span><span class="hljs-variable">$readSockets</span></span><span>, </span><span><span class="hljs-variable">$writeSockets</span></span><span>, </span><span><span class="hljs-variable">$exceptSockets</span></span><span>, </span><span><span class="hljs-number">1</span></span><span>);

    </span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$numChangedSockets</span></span><span> === </span><span><span class="hljs-literal">false</span></span><span>) {
        </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"socket_select 失敗："</span></span><span> . </span><span><span class="hljs-title function_ invoke__">socket_strerror</span></span><span>(</span><span><span class="hljs-title function_ invoke__">socket_last_error</span></span><span>()) . PHP_EOL;
        </span><span><span class="hljs-keyword">break</span></span><span>;
    }

    </span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$readSockets</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$sock</span></span><span>) {
        </span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$sock</span></span><span> === </span><span><span class="hljs-variable">$server</span></span><span>) {
            </span><span><span class="hljs-comment">// 有新的連接</span></span><span>
            </span><span><span class="hljs-variable">$newClient</span></span><span> = </span><span><span class="hljs-title function_ invoke__">socket_accept</span></span><span>(</span><span><span class="hljs-variable">$server</span></span><span>);
            </span><span><span class="hljs-title function_ invoke__">socket_set_nonblock</span></span><span>(</span><span><span class="hljs-variable">$newClient</span></span><span>);
            </span><span><span class="hljs-variable">$clients</span></span><span>[] = </span><span><span class="hljs-variable">$newClient</span></span><span>;
            </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"新客戶端已連接。"</span></span><span> . PHP_EOL;
        } </span><span><span class="hljs-keyword">else</span></span><span> {
            </span><span><span class="hljs-comment">// 有客戶端發來數據</span></span><span>
            </span><span><span class="hljs-variable">$data</span></span><span> = @</span><span><span class="hljs-title function_ invoke__">socket_read</span></span><span>(</span><span><span class="hljs-variable">$sock</span></span><span>, </span><span><span class="hljs-number">1024</span></span><span>, PHP_NORMAL_READ);
            </span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$data</span></span><span> === </span><span><span class="hljs-literal">false</span></span><span> || </span><span><span class="hljs-variable">$data</span></span><span> === </span><span><span class="hljs-string">""</span></span><span>) {
                </span><span><span class="hljs-comment">// 客戶端斷開連接</span></span><span>
                </span><span><span class="hljs-variable">$index</span></span><span> = </span><span><span class="hljs-title function_ invoke__">array_search</span></span><span>(</span><span><span class="hljs-variable">$sock</span></span><span>, </span><span><span class="hljs-variable">$clients</span></span><span>);
                </span><span><span class="hljs-keyword">unset</span></span><span>(</span><span><span class="hljs-variable">$clients</span></span><span>[</span><span><span class="hljs-variable">$index</span></span><span>]);
                </span><span><span class="hljs-title function_ invoke__">socket_close</span></span><span>(</span><span><span class="hljs-variable">$sock</span></span><span>);
                </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"客戶端斷開連接。"</span></span><span> . PHP_EOL;
            } </span><span><span class="hljs-keyword">else</span></span><span> {
                </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"收到數據："</span></span><span> . </span><span><span class="hljs-title function_ invoke__">trim</span></span><span>(</span><span><span class="hljs-variable">$data</span></span><span>) . PHP_EOL;
            }
        }
    }
}
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

要點總結

非阻塞socket ：為避免阻塞主進程，所有socket 都應設置為非阻塞模式。
主socket 檢查連接請求：當socket_select檢測到主socket 可讀，說明有新的客戶端連接請求。
客戶端socket 檢查數據：當某個客戶端socket 可讀時，說明客戶端發送了數據。
注意斷連處理：如果讀取失敗或返回空字符串，應認為客戶端已斷開連接。

結語

socket_select()是處理並發socket 通信的關鍵工具。相比每個連接都起一個線程或進程，使用select模型可以更輕量、可控地管理大量連接。熟練掌握它，會讓你的PHP 網絡應用更穩定、更高效。

希望本文能幫助你理解socket_select的使用場景與實踐方式，並能在你的項目中真正發揮作用。

 <span></span>

socket_select