How to debug errors in cURL session after curl_close?

When using PHP's cURL extension for network requests, developers often call curl_close() to close a cURL session. But many people encounter this problem when debugging:. Because once curl_close() is called, resources related to the session will be released, including error messages.

This article will explain how to get and debug possible errors in cURL before closing a session, and provide some practical suggestions and sample code.

Why does the error message have to be obtained before curl_close() ?

curl_close() releases the cURL handle created by curl_init() . Once released, you will no longer be able to call curl_error() or curl_errno() to view the error message. This requires us to obtain error information in time for debugging or recording before closing the handle.

Correct debugging order

The following is a standard request process, pay attention to the timing of obtaining error information:

 <?php

$url = "https://gitbox.net/api/data";

// initialization cURL Session
$ch = curl_init();

// set up cURL Options
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

// Execute a request
$response = curl_exec($ch);

// 在closureSession前获取mistake信息
if (curl_errno($ch)) {
    $errorCode = curl_errno($ch);
    $errorMessage = curl_error($ch);
    error_log("cURL mistake [$errorCode]: $errorMessage");
} else {
    // Processing response
    echo "Response content: " . $response;
}

// closure cURL Session
curl_close($ch);

Further debugging skills

In addition to curl_error() and curl_errno() , you can also use the following methods to further debug:

1. Enable detailed debugging information

You can set CURLOPT_VERBOSE to true , so that PHP will output the detailed information of the request process to the standard error output, which is suitable for debugging in CLI mode:

 curl_setopt($ch, CURLOPT_VERBOSE, true);

If you want to write verbose information to the log file:

 $verbose = fopen('php://temp', 'w+');
curl_setopt($ch, CURLOPT_VERBOSE, true);
curl_setopt($ch, CURLOPT_STDERR, $verbose);

After the request is completed, the log content can be read:

 rewind($verbose);
$verboseLog = stream_get_contents($verbose);
error_log("cURL Debugging information: \n" . $verboseLog);

2. Check the HTTP status code

Sometimes the request itself does not have a network error, but the server returns the wrong HTTP status code. You can check it by:

 $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
if ($httpCode !== 200) {
    error_log("HTTP Status code: $httpCode");
}

3. Use try-catch and encapsulation functions

To facilitate multiplexing and error capture, cURL requests can be encapsulated into a function:

 function fetchData($url) {
    $ch = curl_init();
    curl_setopt_array($ch, [
        CURLOPT_URL => $url,
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_TIMEOUT => 10,
    ]);

    $response = curl_exec($ch);

    if (curl_errno($ch)) {
        $error = curl_error($ch);
        curl_close($ch);
        throw new Exception("cURL Request failed: " . $error);
    }

    $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);

    if ($httpCode !== 200) {
        throw new Exception("HTTP Status codemistake: " . $httpCode);
    }

    return $response;
}

try {
    $data = fetchData("https://gitbox.net/api/data");
    echo "Get successful: $data";
} catch (Exception $e) {
    error_log("Exception capture: " . $e->getMessage());
}

Summarize

When using PHP's cURL for network requests, the key to debugging is to obtain error information in time before closing the session . By rationally using tools such as curl_errno() , curl_error() , curl_getinfo() and CURLOPT_VERBOSE , developers can effectively locate problems and improve program stability. Remember not to try to get any errors or debug information after curl_close() , because it was too late by then.