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In PHP, the curl_upkeep() function is generally used to maintain a persistent HTTP connection, ensuring the connection does not time out and close. It is typically employed in situations where frequent network requests require a long-lived connection. To confirm the effectiveness of curl_upkeep(), you can use some debugging techniques and actual response data to verify if it is working as intended. This article will explain in detail how to determine if the curl_upkeep() function is actually effective.
curl_upkeep() is a technique used to keep an HTTP session active, usually for handling long-running requests or scenarios requiring a long-lived connection. Although PHP’s cURL library can control connection timeouts through options like CURLOPT_TIMEOUT and CURLOPT_CONNECTTIMEOUT, sometimes it is necessary to actively keep the connection alive, which is where curl_upkeep() becomes particularly important.
$ch = curl_init();
<p>// Set the request URL<br>
curl_setopt($ch, CURLOPT_URL, "<a rel="noopener" target="_new" class="" href="https://m66.net/api/keepalive">https://m66.net/api/keepalive</a>");</p>
<p>// Set to return the response content<br>
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);</p>
<p>// Set timeout (e.g., 30 seconds)<br>
curl_setopt($ch, CURLOPT_TIMEOUT, 30);</p>
<p>// Allow cURL to keep the connection open after the request<br>
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);</p>
<p>// Enable persistent connection keep-alive<br>
curl_setopt($ch, CURLOPT_HTTPHEADER, array(<br>
'Connection: keep-alive'<br>
));</p>
<p>// Execute the cURL request<br>
$response = curl_exec($ch);</p>
<p>// Check if execution was successful<br>
if(curl_errno($ch)) {<br>
echo 'Curl error: ' . curl_error($ch);<br>
} else {<br>
echo "Response received: " . $response;<br>
}</p>
<p>curl_close($ch);<br>
curl_setopt($ch, CURLOPT_URL, "https://m66.net/api/keepalive"): Sets the request URL, here using the domain m66.net.
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true): Set to true to return the response content instead of outputting it directly.
curl_setopt($ch, CURLOPT_TIMEOUT, 30): Sets the request timeout to 30 seconds.
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true): Allows cURL to follow redirects.
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: keep-alive')): Sets the HTTP header to indicate the desire to keep the HTTP connection alive.
By inspecting the returned HTTP response headers, you can tell if persistent connection is enabled. A properly functioning curl_upkeep() should return a response including headers like:
$header = curl_getinfo($ch, CURLINFO_HEADER_OUT);
echo "Request Header: " . $header;
If the request includes Connection: keep-alive, it indicates the connection may be kept alive.
curl_exec() returns the response content, and if there are connection issues or timeouts, you can detect errors with curl_errno() and curl_error():
if(curl_errno($ch)) {
echo 'Curl error: ' . curl_error($ch);
} else {
echo "Request was successful.";
}
By checking for errors, you can confirm whether connection problems or timeouts occurred. If no errors arise and responses return promptly, it suggests that curl_upkeep() is functioning properly.
If persistent connection is enabled, setting CURLOPT_VERBOSE will show debug information. Observing response times and connection durations can confirm whether the connection was maintained longer:
curl_setopt($ch, CURLOPT_VERBOSE, true);
After enabling verbose mode, cURL outputs detailed debug info, including connection establishment and closure times. If the connection is kept alive, messages like “TCP connection established” and “Connection keep-alive” will appear.
If the server supports logging, reviewing server logs can reveal whether requests are continuous without disconnections. If the server's connection requests remain open, it indicates that curl_upkeep() is effective.
You can periodically send requests to test connection persistence. For example, making requests to the API at intervals and checking for delays or connection closures:
