【mysql_field_len搭配mysql_fetch_field一起怎麼用？來看示例講解】

gitbox 2025-09-23

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 這裡是與文章內容無關的PHP代碼示例</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"歡迎閱讀本篇文章！&lt;br&gt;"</span></span><span>;
</span><span><span class="hljs-title function_ invoke__">date_default_timezone_set</span></span><span>(</span><span><span class="hljs-string">'Asia/Shanghai'</span></span><span>);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"當前時間："</span></span><span> . </span><span><span class="hljs-title function_ invoke__">date</span></span><span>(</span><span><span class="hljs-string">'Y-m-d H:i:s'</span></span><span>) . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
</span><span><span class="hljs-meta">?&gt;</span></span><span>

&lt;hr&gt;

</span><span><span class="hljs-meta">&lt;?php</span></span><span>
<span class="hljs-comment">/*
文章標題：【mysql_field_len搭配mysql_fetch_field一起怎麼用？來看示例講解】
*/</span>

</span><span><span class="hljs-comment">// 在使用PHP操作MySQL數據庫時，很多人會遇到需要獲取字段長度的需求。</span></span><span>
</span><span><span class="hljs-comment">// 這裡我們重點講解mysql_field_len函數如何與mysql_fetch_field搭配使用。</span></span><span>

</span><span><span class="hljs-comment">// 1. 連接數據庫</span></span><span>
</span><span><span class="hljs-variable">$conn</span></span><span> = </span><span><span class="hljs-title function_ invoke__">mysql_connect</span></span><span>(</span><span><span class="hljs-string">'localhost'</span></span><span>, </span><span><span class="hljs-string">'root'</span></span><span>, </span><span><span class="hljs-string">'password'</span></span><span>);
</span><span><span class="hljs-keyword">if</span></span><span> (!</span><span><span class="hljs-variable">$conn</span></span><span>) {
    </span><span><span class="hljs-keyword">die</span></span><span>(</span><span><span class="hljs-string">'數據庫連接失敗: '</span></span><span> . </span><span><span class="hljs-title function_ invoke__">mysql_error</span></span><span>());
}
</span><span><span class="hljs-title function_ invoke__">mysql_select_db</span></span><span>(</span><span><span class="hljs-string">'test_db'</span></span><span>, </span><span><span class="hljs-variable">$conn</span></span><span>);

</span><span><span class="hljs-comment">// 2. 執行查詢</span></span><span>
</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">mysql_query</span></span><span>(</span><span><span class="hljs-string">'SELECT id, username, email FROM users'</span></span><span>);
</span><span><span class="hljs-keyword">if</span></span><span> (!</span><span><span class="hljs-variable">$result</span></span><span>) {
    </span><span><span class="hljs-keyword">die</span></span><span>(</span><span><span class="hljs-string">'查詢失敗: '</span></span><span> . </span><span><span class="hljs-title function_ invoke__">mysql_error</span></span><span>());
}

</span><span><span class="hljs-comment">// 3. 使用mysql_fetch_field獲取字段信息</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"&lt;h3&gt;字段信息列表：&lt;/h3&gt;"</span></span><span>;
</span><span><span class="hljs-keyword">while</span></span><span> (</span><span><span class="hljs-variable">$field</span></span><span> = </span><span><span class="hljs-title function_ invoke__">mysql_fetch_field</span></span><span>(</span><span><span class="hljs-variable">$result</span></span><span>)) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"字段名: "</span></span><span> . </span><span><span class="hljs-variable">$field</span></span><span>-&gt;name . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"字段類型: "</span></span><span> . </span><span><span class="hljs-variable">$field</span></span><span>-&gt;type . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    </span><span><span class="hljs-comment">// 4. 使用mysql_field_len獲取字段長度</span></span><span>
    </span><span><span class="hljs-variable">$length</span></span><span> = </span><span><span class="hljs-title function_ invoke__">mysql_field_len</span></span><span>(</span><span><span class="hljs-variable">$result</span></span><span>, </span><span><span class="hljs-variable">$field</span></span><span>-&gt;orgname ? </span><span><span class="hljs-variable">$field</span></span><span>-&gt;orgname : </span><span><span class="hljs-variable">$field</span></span><span>-&gt;name);
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"字段長度: "</span></span><span> . </span><span><span class="hljs-variable">$length</span></span><span> . </span><span><span class="hljs-string">"&lt;br&gt;&lt;hr&gt;"</span></span><span>;
}

<span class="hljs-comment">/*
注意事項：
1. mysql_* 系列函數在 PHP 7 及以上版本已被棄用，建議使用 mysqli 或 PDO。
2. mysql_field_len 返回字段的最大字節長度，而不是字符數，對於多字節字符集需要注意。
3. mysql_fetch_field 可以獲取字段的詳細信息，包括類型、長度、默認值等。
*/</span>

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

<hr>

 <span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 尾部无关代碼示例</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"感謝閱讀本文！&lt;br&gt;"</span></span><span>;
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

mysql_field_len