如何結合mysqli::debug 和error_log 一起輸出詳細調試信息？

gitbox 2025-09-15

如何結合mysqli::debug和error_log一起輸出詳細調試信息？

在開發PHP 項目時，數據庫操作往往是最容易出錯的地方。為了能夠快速定位問題，詳細的調試信息是不可或缺的。 PHP 的mysqli擴展提供了一些有用的調試功能，特別是mysqli::debug方法，可以幫助開發者獲取MySQL 的調試信息。與此同時， error_log函數則是一個將錯誤日誌寫入文件、系統日誌或發送到郵件的有力工具。結合這兩者，開發者可以實現更全面、更直觀的數據庫調試日誌輸出。

1. mysqli::debug簡介

mysqli::debug是mysqli類中的一個方法，它可以輸出MySQL 數據庫的底層調試信息。通過使用該方法，開發者可以查看執行的SQL 查詢、連接信息以及MySQL 服務器的狀態等。這對於調試SQL 查詢的執行過程非常有幫助。

使用mysqli::debug非常簡單，只需要在適當的位置調用它即可。以下是一個簡單的使用示例：

 <span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$mysqli</span></span><span> = </span><span><span class="hljs-keyword">new</span></span><span> </span><span><span class="hljs-title function_ invoke__">mysqli</span></span><span>(</span><span><span class="hljs-string">"localhost"</span></span><span>, </span><span><span class="hljs-string">"username"</span></span><span>, </span><span><span class="hljs-string">"password"</span></span><span>, </span><span><span class="hljs-string">"database"</span></span><span>);

</span><span><span class="hljs-comment">// 開啟調試模式</span></span><span>
</span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">debug</span></span><span>(</span><span><span class="hljs-string">"d:t"</span></span><span>); </span><span><span class="hljs-comment">// 'd' 表示調試信息，'t' 表示追踪信息</span></span><span>

</span><span><span class="hljs-comment">// 執行 SQL 查詢</span></span><span>
</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">query</span></span><span>(</span><span><span class="hljs-string">"SELECT * FROM users"</span></span><span>);

</span><span><span class="hljs-comment">// 检查查詢结果</span></span><span>
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$result</span></span><span>) {
    </span><span><span class="hljs-keyword">while</span></span><span> (</span><span><span class="hljs-variable">$row</span></span><span> = </span><span><span class="hljs-variable">$result</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">fetch_assoc</span></span><span>()) {
        </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"User: "</span></span><span> . </span><span><span class="hljs-variable">$row</span></span><span>[</span><span><span class="hljs-string">'name'</span></span><span>] . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    }
} </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">"Query failed: "</span></span><span> . </span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;error;
}
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

在這個例子中， $mysqli->debug("d:t")會啟用調試信息輸出。這些信息將直接輸出到瀏覽器或終端，幫助開發者了解MySQL 查詢的執行細節。

2. error_log簡介

error_log是PHP 內置的一個函數，它可以將錯誤信息發送到系統日誌、指定文件或通過郵件發送給管理員。這個函數非常有用，可以幫助開發者記錄錯誤信息，並且可以根據需要指定日誌的保存位置。

基本的error_log使用方式如下：

 <span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 將錯誤信息記錄到指定文件</span></span><span>
</span><span><span class="hljs-title function_ invoke__">error_log</span></span><span>(</span><span><span class="hljs-string">"Database query failed: "</span></span><span> . </span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;error, </span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-string">"/path/to/your/logfile.log"</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

在這個例子中， error_log將錯誤信息追加到指定的日誌文件中。

3. 結合使用mysqli::debug和error_log

雖然mysqli::debug能夠輸出詳細的數據庫調試信息，但這些信息直接輸出到瀏覽器上可能並不總是理想的，尤其是在生產環境中。因此，將這些信息同時輸出到日誌文件中進行存儲，以便後續分析，是一種更好的做法。

可以結合mysqli::debug和error_log實現更靈活的調試輸出。以下是一個實際的例子：

 <span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 設置調試輸出到日誌文件</span></span><span>
</span><span><span class="hljs-variable">$logFile</span></span><span> = </span><span><span class="hljs-string">'/path/to/your/logfile.log'</span></span><span>;
</span><span><span class="hljs-variable">$mysqli</span></span><span> = </span><span><span class="hljs-keyword">new</span></span><span> </span><span><span class="hljs-title function_ invoke__">mysqli</span></span><span>(</span><span><span class="hljs-string">"localhost"</span></span><span>, </span><span><span class="hljs-string">"username"</span></span><span>, </span><span><span class="hljs-string">"password"</span></span><span>, </span><span><span class="hljs-string">"database"</span></span><span>);

</span><span><span class="hljs-comment">// 開啟調試模式</span></span><span>
</span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">debug</span></span><span>(</span><span><span class="hljs-string">"d:t"</span></span><span>);

</span><span><span class="hljs-comment">// 記錄調試信息到日誌文件</span></span><span>
</span><span><span class="hljs-title function_ invoke__">ob_start</span></span><span>(); </span><span><span class="hljs-comment">// 開啟輸出緩衝</span></span><span>
</span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">debug</span></span><span>(</span><span><span class="hljs-string">"d:t"</span></span><span>);
</span><span><span class="hljs-variable">$debugOutput</span></span><span> = </span><span><span class="hljs-title function_ invoke__">ob_get_clean</span></span><span>();

</span><span><span class="hljs-comment">// 將調試信息輸出到指定日誌文件</span></span><span>
</span><span><span class="hljs-keyword">if</span></span><span> (!</span><span><span class="hljs-keyword">empty</span></span><span>(</span><span><span class="hljs-variable">$debugOutput</span></span><span>)) {
    </span><span><span class="hljs-title function_ invoke__">error_log</span></span><span>(</span><span><span class="hljs-string">"MySQL Debug Output: "</span></span><span> . </span><span><span class="hljs-variable">$debugOutput</span></span><span>, </span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-variable">$logFile</span></span><span>);
}

</span><span><span class="hljs-comment">// 執行 SQL 查詢</span></span><span>
</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">query</span></span><span>(</span><span><span class="hljs-string">"SELECT * FROM users"</span></span><span>);

</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$result</span></span><span>) {
    </span><span><span class="hljs-keyword">while</span></span><span> (</span><span><span class="hljs-variable">$row</span></span><span> = </span><span><span class="hljs-variable">$result</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">fetch_assoc</span></span><span>()) {
        </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"User: "</span></span><span> . </span><span><span class="hljs-variable">$row</span></span><span>[</span><span><span class="hljs-string">'name'</span></span><span>] . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    }
} </span><span><span class="hljs-keyword">else</span></span><span> {
    </span><span><span class="hljs-variable">$errorMsg</span></span><span> = </span><span><span class="hljs-string">"Query failed: "</span></span><span> . </span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;error;
    </span><span><span class="hljs-comment">// 記錄 SQL 錯誤信息到日誌文件</span></span><span>
    </span><span><span class="hljs-title function_ invoke__">error_log</span></span><span>(</span><span><span class="hljs-variable">$errorMsg</span></span><span>, </span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-variable">$logFile</span></span><span>);
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$errorMsg</span></span><span>;
}
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

在上面的代碼中，我們首先通過mysqli::debug啟用調試信息，並利用ob_start和ob_get_clean捕獲這些信息。然後通過error_log將調試輸出記錄到指定的日誌文件中。在SQL 查詢執行後，如果查詢失敗，我們還會記錄錯誤信息到同一個日誌文件。

4. 優化日誌記錄

在生產環境中，過多的調試信息可能會使日誌文件迅速變得龐大，影響系統性能。因此，我們可以根據環境條件（如開發環境與生產環境）來靈活調整調試輸出。

例如，在開發環境中開啟詳細的調試信息，而在生產環境中關閉：

 <span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$mysqli</span></span><span> = </span><span><span class="hljs-keyword">new</span></span><span> </span><span><span class="hljs-title function_ invoke__">mysqli</span></span><span>(</span><span><span class="hljs-string">"localhost"</span></span><span>, </span><span><span class="hljs-string">"username"</span></span><span>, </span><span><span class="hljs-string">"password"</span></span><span>, </span><span><span class="hljs-string">"database"</span></span><span>);

</span><span><span class="hljs-comment">// 开发环境下開啟調試模式</span></span><span>
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-title function_ invoke__">getenv</span></span><span>(</span><span><span class="hljs-string">'ENVIRONMENT'</span></span><span>) === </span><span><span class="hljs-string">'development'</span></span><span>) {
    </span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">debug</span></span><span>(</span><span><span class="hljs-string">"d:t"</span></span><span>);
}

</span><span><span class="hljs-comment">// 執行 SQL 查詢</span></span><span>
</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">query</span></span><span>(</span><span><span class="hljs-string">"SELECT * FROM users"</span></span><span>);

</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$result</span></span><span>) {
    </span><span><span class="hljs-keyword">while</span></span><span> (</span><span><span class="hljs-variable">$row</span></span><span> = </span><span><span class="hljs-variable">$result</span></span><span>-&gt;</span><span><span class="hljs-title function_ invoke__">fetch_assoc</span></span><span>()) {
        </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"User: "</span></span><span> . </span><span><span class="hljs-variable">$row</span></span><span>[</span><span><span class="hljs-string">'name'</span></span><span>] . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    }
} </span><span><span class="hljs-keyword">else</span></span><span> {
    </span><span><span class="hljs-variable">$errorMsg</span></span><span> = </span><span><span class="hljs-string">"Query failed: "</span></span><span> . </span><span><span class="hljs-variable">$mysqli</span></span><span>-&gt;error;
    </span><span><span class="hljs-title function_ invoke__">error_log</span></span><span>(</span><span><span class="hljs-variable">$errorMsg</span></span><span>, </span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-string">"/path/to/your/logfile.log"</span></span><span>);
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$errorMsg</span></span><span>;
}
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

5. 總結

通過結合使用mysqli::debug和error_log ，開發者可以有效地捕獲和記錄MySQL 數據庫的調試信息，並將其輸出到日誌文件中，方便後續分析和問題定位。在開發環境中，調試信息可以幫助開發人員快速識別問題，而在生產環境中，合理的日誌記錄能確保系統穩定運行的同時，也能方便地回溯和解決潛在問題。

相關標籤:
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