如何使用feof配合ob_flush和flush函数实现大文件的分段输出？

<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// 以下部分与文章内容无关，仅为示例前置代码</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<!-- 页面开始 -->\n"</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-title function_ invoke__">ob_start</span></span><span>();
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</span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// 正文开始</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<h1>如何使用feof配合ob_flush和flush函数实现大文件的分段输出？</h1>"</span></span><span>;

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<p>在处理大文件下载或者生成大文件内容时，如果一次性将整个文件内容输出到浏览器，容易导致PHP内存溢出或网页长时间无响应。为了避免这种情况，可以采用分段输出的方式，即每次输出一部分内容，然后刷新缓冲区，让浏览器逐步接收到数据。</p>"</span></span><span>;

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<h2>关键函数说明</h2>"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<ul>"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<li><strong>feof(resource <span class="hljs-subst">$handle</span></span></span><span>)</strong>：检查文件指针是否到达文件末尾。如果到达末尾返回 true，否则返回 false。</li>";
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<li><strong>ob_flush()</strong>：将 PHP 的输出缓冲区内容发送到浏览器，并清空缓冲区（需要开启缓冲区）。</li>"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<li><strong>flush()</strong>：强制将服务器缓冲区中的内容发送到浏览器，使浏览器立即显示输出。</li>"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"</ul>"</span></span><span>;

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<h2>实现思路</h2>"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<ol>"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<li>打开要输出的文件，并判断是否成功。</li>"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<li>循环读取文件内容，可以按行或者按固定字节数读取。</li>"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"<li>在每次读取输出后，调用 <code>ob_flush()