curl_init 与 curl_setopt 实现文件下载进度回调

<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// 前言部分，与正文内容无关</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"这是一个示例程序，用于演示PHP中的基本输出和函数使用。<br>"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"程序开始执行...<br>"</span></span><span>;
</span><span><span class="hljs-comment">// 更多无关代码</span></span><span>
</span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">dummyFunction</span></span><span>(</span><span><span class="hljs-params"></span></span><span>) {
    </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-string">"这只是一个占位函数，与文章主题无关。"</span></span><span>;
}
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">dummyFunction</span></span><span>();
</span><span><span class="hljs-meta">?></span></span><span>

<hr>

</span><span><span class="hljs-meta"><?php</span></span><span>
<span class="hljs-comment">/*
文章正文: curl_init 与 curl_setopt 实现文件下载进度回调
*/</span>

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<h2>使用 PHP cURL 实现文件下载并显示进度回调</h2>"</span></span><span>;

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<p>在 PHP 中，我们可以通过 <code>curl_init