How to Properly Use the curl_multi_select Function for Multi-Threaded Concurrent Requests: Step-by-Step Guide and Key Considerations

<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// Example of irrelevant pre-code</span></span><span>
</span><span><span class="hljs-variable">$timestamp</span></span><span> = </span><span><span class="hljs-title function_ invoke__">time</span></span><span>();
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Current timestamp: "</span></span><span> . </span><span><span class="hljs-variable">$timestamp</span></span><span> . </span><span><span class="hljs-string">"\n"</span></span><span>;
<p></span>$dummyArray = array_fill(0, 5, "test");<br>
foreach ($dummyArray as $item) {<br>
echo "Array element: " . $item . "\n";<br>
}</p>
<p>echo "Initialization complete.\n";<br>
?></p>
<p><hr></p>
<p><?php<br>
// Start of main article<br>
echo "<h1>How to Properly Use the curl_multi_select Function for Multi-Threaded Concurrent Requests: Step-by-Step Guide and Key Considerations</h1>";</p>
<p>echo "<p>In PHP, making multiple HTTP requests sequentially is highly inefficient. By using the <strong>curl_multi</strong> functions, you can perform concurrent requests, greatly improving efficiency. Among these, <strong>curl_multi_select</strong> is a crucial function that efficiently waits for activity on multiple cURL handles, preventing CPU idle waste.</p>";</p>
<p>echo "<h2>1. Basic Concepts</h2>";<br>
echo "<ul><br>
<li><strong>curl_multi_init()</strong>: Initializes a cURL multi-handle.</li><br>
<li><strong>curl_multi_add_handle()</strong>: Adds a single cURL handle to the multi-handle.</li><br>
<li><strong>curl_multi_exec()</strong>: Executes all added cURL handles.</li><br>
<li><strong>curl_multi_select()</strong>: Blocks until a cURL handle has activity, preventing CPU busy-waiting.</li><br>
<li><strong>curl_multi_getcontent()</strong>: Retrieves the content of a single request.</li><br>
<li><strong>curl_multi_remove_handle()</strong>: Removes a single cURL handle.</li><br>
<li><strong>curl_multi_close()</strong>: Closes the multi-handle.</li><br>
</ul>";</p>
<p data-is-last-node="" data-is-only-node="">echo "<h2>2. Step-by-Step Instructions</h2>";<br>
echo<span> <span class="hljs-string">"<ol><br>
<li><strong>Initialize the multi-handle:</strong><br><br>
<code>$mh = curl_multi_init();