【mysql_field_len搭配mysql_fetch_field一起怎么用？来看示例讲解】

gitbox 2025-09-23

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 这里是与文章内容无关的PHP代码示例</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"欢迎阅读本篇文章！&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">"当前时间："</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>;
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&lt;hr&gt;

</span><span><span class="hljs-meta">&lt;?php</span></span><span>
<span class="hljs-comment">/*
文章标题：【mysql_field_len搭配mysql_fetch_field一起怎么用？来看示例讲解】
*/</span>

</span><span><span class="hljs-comment">// 在使用PHP操作MySQL数据库时，很多人会遇到需要获取字段长度的需求。</span></span><span>
</span><span><span class="hljs-comment">// 这里我们重点讲解mysql_field_len函数如何与mysql_fetch_field搭配使用。</span></span><span>

</span><span><span class="hljs-comment">// 1. 连接数据库</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">'数据库连接失败: '</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. 执行查询</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">'查询失败: '</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获取字段信息</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">$field</span></span><span>-&gt;name . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"字段类型: "</span></span><span> . </span><span><span class="hljs-variable">$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获取字段长度</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">$field</span></span><span>-&gt;name);
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"字段长度: "</span></span><span> . </span><span><span class="hljs-variable">$length</span></span><span> . </span><span><span class="hljs-string">"&lt;br&gt;&lt;hr&gt;"</span></span><span>;
}

<span class="hljs-comment">/*
注意事项：
1. mysql_* 系列函数在 PHP 7 及以上版本已被弃用，建议使用 mysqli 或 PDO。
2. mysql_field_len 返回字段的最大字节长度，而不是字符数，对于多字节字符集需要注意。
3. mysql_fetch_field 可以获取字段的详细信息，包括类型、长度、默认值等。
*/</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">// 尾部无关代码示例</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"感谢阅读本文！&lt;br&gt;"</span></span><span>;
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

mysql_field_len