dns_get_record函數的基本用法有哪些？如何在PHP中高效使用dns_get_record？

gitbox 2025-06-27

在PHP中， dns_get_record()函數是一個非常實用的工具，用於獲取指定域名的DNS 記錄信息。這個函數為開發者提供了直接從DNS 服務器查詢記錄的能力，廣泛應用於網絡診斷、郵件系統開發、域名工具平台等場景。

一、dns_get_record的基本用法

dns_get_record()的函數原型如下：

 <span><span><span class="hljs-keyword">array</span></span><span> </span><span><span class="hljs-title function_ invoke__">dns_get_record</span></span><span> ( </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$hostname</span></span><span> [, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$type</span></span><span> = DNS_ANY [, </span><span><span class="hljs-keyword">array</span></span><span> &amp;</span><span><span class="hljs-variable">$authns</span></span><span> [, </span><span><span class="hljs-keyword">array</span></span><span> &amp;</span><span><span class="hljs-variable">$addtl</span></span><span> ]]] )
</span></span>

$hostname ：要查詢的主機名（例如： example.com ）。
$type ：查詢的DNS 記錄類型。常用的類型包括：
- DNS_A ：IPv4 地址
- DNS_AAAA ：IPv6 地址
- DNS_MX ：郵件交換記錄
- DNS_CNAME ：別名記錄
- DNS_TXT ：文本記錄
- DNS_NS ：域名服務器
- DNS_SOA ：起始授權機構記錄
- DNS_ANY ：所有類型的記錄
$authns （可選）：返回權威名稱服務器信息。
$addtl （可選）：返回附加記錄。

示例1：查詢A 記錄

<span><span><span class="hljs-variable">$records</span></span><span> = </span><span><span class="hljs-title function_ invoke__">dns_get_record</span></span><span>(</span><span><span class="hljs-string">"example.com"</span></span><span>, DNS_A);
</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$records</span></span><span>);
</span></span>

這段代碼將返回一個包含所有A 記錄的數組，每個元素是一個關聯數組，包含如host , type , ip , ttl等字段。

示例2：查詢MX 記錄

<span><span><span class="hljs-variable">$mxRecords</span></span><span> = </span><span><span class="hljs-title function_ invoke__">dns_get_record</span></span><span>(</span><span><span class="hljs-string">"example.com"</span></span><span>, DNS_MX);
</span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$mxRecords</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$record</span></span><span>) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Mail Server: <span class="hljs-subst">{$record['target']}</span></span></span><span>, Priority: </span><span><span class="hljs-subst">{$record['pri']}</span></span><span>\n";
}
</span></span>

二、高效使用dns_get_record 的技巧

為了更高效地使用該函數，有以下幾個實用技巧和建議：

1. 明確記錄類型

避免使用DNS_ANY ，因為這會一次性請求所有類型的記錄，可能會產生額外的性能開銷。在實際使用中，應只查詢所需的記錄類型。

2. 利用緩存減少重複查詢

dns_get_record()並不會緩存結果，每次調用都會執行真正的DNS 查詢。如果在一個應用生命週期中需要重複查詢同一個域名，建議配合緩存機制（如APCu 或Memcached）使用：

 <span><span><span class="hljs-variable">$cacheKey</span></span><span> = </span><span><span class="hljs-string">'dns_a_example_com'</span></span><span>;
</span><span><span class="hljs-variable">$records</span></span><span> = </span><span><span class="hljs-title function_ invoke__">apcu_fetch</span></span><span>(</span><span><span class="hljs-variable">$cacheKey</span></span><span>);

</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$records</span></span><span> === </span><span><span class="hljs-literal">false</span></span><span>) {
    </span><span><span class="hljs-variable">$records</span></span><span> = </span><span><span class="hljs-title function_ invoke__">dns_get_record</span></span><span>(</span><span><span class="hljs-string">"example.com"</span></span><span>, DNS_A);
    </span><span><span class="hljs-title function_ invoke__">apcu_store</span></span><span>(</span><span><span class="hljs-variable">$cacheKey</span></span><span>, </span><span><span class="hljs-variable">$records</span></span><span>, </span><span><span class="hljs-number">300</span></span><span>); </span><span><span class="hljs-comment">// 快取5分鐘</span></span><span>
}
</span></span>

3. 錯誤處理與結果驗證

dns_get_record()查詢失敗時會返回false ，因此在生產環境中應始終進行返回值檢查：

 <span><span><span class="hljs-variable">$records</span></span><span> = </span><span><span class="hljs-title function_ invoke__">dns_get_record</span></span><span>(</span><span><span class="hljs-string">"example.com"</span></span><span>, DNS_MX);
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$records</span></span><span> === </span><span><span class="hljs-literal">false</span></span><span>) {
    </span><span><span class="hljs-title function_ invoke__">error_log</span></span><span>(</span><span><span class="hljs-string">"DNS 查詢失敗"</span></span><span>);
    </span><span><span class="hljs-comment">// 可根據需求進行回退機製或用戶提示</span></span><span>
}
</span></span>

4. 分析不同類型字段

不同類型的DNS 記錄字段略有不同。例如， A記錄中是ip字段，而MX記錄中有pri和target ，在處理這些數據時應注意結構差異：

 <span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$records</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$record</span></span><span>) {
    </span><span><span class="hljs-keyword">switch</span></span><span> (</span><span><span class="hljs-variable">$record</span></span><span>[</span><span><span class="hljs-string">'type'</span></span><span>]) {
        </span><span><span class="hljs-keyword">case</span></span><span> </span><span><span class="hljs-string">'A'</span></span><span>:
            </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"IP: "</span></span><span> . </span><span><span class="hljs-variable">$record</span></span><span>[</span><span><span class="hljs-string">'ip'</span></span><span>] . </span><span><span class="hljs-string">"\n"</span></span><span>;
            </span><span><span class="hljs-keyword">break</span></span><span>;
        </span><span><span class="hljs-keyword">case</span></span><span> </span><span><span class="hljs-string">'MX'</span></span><span>:
            </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"MX: "</span></span><span> . </span><span><span class="hljs-variable">$record</span></span><span>[</span><span><span class="hljs-string">'target'</span></span><span>] . </span><span><span class="hljs-string">" (Priority: "</span></span><span> . </span><span><span class="hljs-variable">$record</span></span><span>[</span><span><span class="hljs-string">'pri'</span></span><span>] . </span><span><span class="hljs-string">")\n"</span></span><span>;
            </span><span><span class="hljs-keyword">break</span></span><span>;
    }
}
</span></span>

三、總結

PHP 的dns_get_record()函數提供了直接訪問域名解析記錄的方式，非常適合需要動態DNS 查詢的場景。通過合理地設置查詢類型、加入緩存機制和結構化解析返回值，可以在實際應用中更加高效、安全地使用這一函數。在開發與DNS 相關的功能時， dns_get_record()是不可或缺的利器。

dns_get_record