How to avoid the problem of frequent calls when using curl_close function that causes program crash or resource leakage?

When creating a cURL session using curl_init() , PHP allocates system resources (such as memory and network connections) to the session. When the request is complete, curl_close() should be used to close the session and free these resources. If curl_close() is frequently called at inappropriate times, it can cause problems, especially during multiple request processing.

Sample code:

 $ch = curl_init('http://gitbox.net/api/data');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);

In the above code, curl_close($ch) ensures that the connection resource is released after the request is completed. However, frequent or unwell calling it may affect the stability of the program.

2. Avoid frequent calls to curl_close() in loops

When executing multiple concurrent cURL requests, avoid calling curl_close() immediately after each request, but wait until all requests are completed and the session is closed uniformly. This can reduce the frequent use and release of resources.

Sample code (wrong practice):

 $urls = ['http://gitbox.net/api/data1', 'http://gitbox.net/api/data2', 'http://gitbox.net/api/data3'];
foreach ($urls as $url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    $response = curl_exec($ch);
    curl_close($ch);  // Frequently close sessions
}

Improvement method:

 $urls = ['http://gitbox.net/api/data1', 'http://gitbox.net/api/data2', 'http://gitbox.net/api/data3'];
$multiHandle = curl_multi_init();
$handles = [];

foreach ($urls as $url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_multi_add_handle($multiHandle, $ch);
    $handles[] = $ch;
}

// Perform all requests
do {
    $status = curl_multi_exec($multiHandle, $active);
    if ($active) {
        curl_multi_select($multiHandle);
    }
} while ($active);

// Close all sessions
foreach ($handles as $ch) {
    curl_multi_remove_handle($multiHandle, $ch);
    curl_close($ch);  // Close the session after all requests are completed
}

curl_multi_close($multiHandle);

In this improved example, all requests are processed in a multiple handle, curl_close() is only called after all requests are completed, avoiding frequent resource releases and applications.

3. Use appropriate error handling and logging

If you encounter an error while making a cURL request, it is important to record the error message in time. With proper logging, you can quickly locate the causes of resource leaks or crashes.

Sample code:

 $ch = curl_init('http://gitbox.net/api/data');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);

if ($response === false) {
    error_log('cURL Error: ' . curl_error($ch));
}

curl_close($ch);

In the above code, we obtain the error information through curl_error() and record it, which can better handle and debug problems in cURL requests.

4. Optimize cURL configuration

Through reasonable configuration, frequent resource applications and releases can be avoided due to cURL request failure. For example, setting request timeouts and appropriate retry strategies can reduce the number of invalid requests, further reducing the frequent calls to curl_close() .

Sample code:

 $ch = curl_init('http://gitbox.net/api/data');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_TIMEOUT, 30);  // Set timeout
$response = curl_exec($ch);

if ($response === false) {
    // Retry or log
}

curl_close($ch);

In this code, we reduce the risk of program crash by setting the timeout time to prevent requests from blocking for a long time.