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Curl_multi_close code optimization: How to reduce unnecessary calls

gitbox 2025-05-12

When using PHP's cURL extension for multi-request processing, the curl_multi_* series functions are very important, especially curl_multi_close . However, many developers often unconsciously call curl_multi_close over or incorrectly in actual projects, resulting in performance degradation and even waste of resources. So, why do we need to reduce unnecessary curl_multi_close calls? How to make it more efficient?

Why reduce unnecessary curl_multi_close calls?

The main function of curl_multi_close is to close a multi-handle resource created by curl_multi_init . Each time curl_multi_close is called, the PHP underlying layer performs resource release operations, including cleaning up all internal states associated with it. Although this overhead may seem negligible for small-scale requests, frequent and meaningless creation and closing of multi-handle resources in high-concurrency, large-scale request environments can cause the following problems:

  • Performance overhead : Each shutdown involves the release and management of underlying system resources, increasing the CPU and memory burden.

  • Resource waste : Repeated creation and destruction leads to significant fluctuations in memory and connection resources occupied by the program.

  • Potential stability problems : Frequent release of resources may cause difficult-to-trace exceptions, especially when the number of requests is large, connection errors, request failures and other problems are prone to occur.

  • Reduce concurrency performance : Because of frequent switching resources, the processing speed is slowed down, which violates the original intention of using curl_multi_* - efficient concurrent processing.

Therefore, reducing unnecessary curl_multi_close calls can significantly improve the stability and overall performance of the application.

How to do it more efficiently?

To optimize the use of curl_multi_close , the key is to control the life cycle of multi-handle resources and reasonably manage the timing of creation and destruction. Here are some practical optimization suggestions:

1. Try to reuse curl_multi_handle

When logically permits, multiplexing the same multi handle to manage multiple requests instead of recreating one every time. You can create a multi handle during the initialization phase, add requests in batches, and close them uniformly after batch execution.

Sample code:

 <?php

// initialization multi handle
$multiHandle = curl_multi_init();

$urls = [
    'https://gitbox.net/api/user/1',
    'https://gitbox.net/api/user/2',
    'https://gitbox.net/api/user/3',
];

$curlHandles = [];

foreach ($urls as $url) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    curl_multi_add_handle($multiHandle, $ch);
    $curlHandles[] = $ch;
}

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

// Get results
foreach ($curlHandles as $ch) {
    $response = curl_multi_getcontent($ch);
    echo $response . PHP_EOL;

    curl_multi_remove_handle($multiHandle, $ch);
    curl_close($ch);
}

// Close only at the end multi handle
curl_multi_close($multiHandle);

?>

2. Avoid closing immediately after each small batch request

Many developers habitually curl_multi_close after each small batch of requests is completed, which will lead to frequent switching resources. Better to do this is to close all batches uniformly after they are completed , or centrally processed at a reasonable batch size (such as a group of 100 requests).

3. Integrate connection pools or management classes to encapsulate resources

If your application needs to initiate multiple requests, consider using a connection pool or a dedicated MultiCurlManager class to manage the life cycle of the multi handle.

Simple example:

 <?php

class MultiCurlManager
{
    private $multiHandle;
    private $handles = [];

    public function __construct()
    {
        $this->multiHandle = curl_multi_init();
    }

    public function addRequest(string $url)
    {
        $ch = curl_init($url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_multi_add_handle($this->multiHandle, $ch);
        $this->handles[] = $ch;
    }

    public function execute()
    {
        do {
            $status = curl_multi_exec($this->multiHandle, $active);
            curl_multi_select($this->multiHandle);
        } while ($active);

        $responses = [];
        foreach ($this->handles as $ch) {
            $responses[] = curl_multi_getcontent($ch);
            curl_multi_remove_handle($this->multiHandle, $ch);
            curl_close($ch);
        }

        return $responses;
    }

    public function __destruct()
    {
        curl_multi_close($this->multiHandle);
    }
}

// use
$manager = new MultiCurlManager();
$manager->addRequest('https://gitbox.net/api/data1');
$manager->addRequest('https://gitbox.net/api/data2');
$manager->addRequest('https://gitbox.net/api/data3');

$responses = $manager->execute();
foreach ($responses as $response) {
    echo $response . PHP_EOL;
}

?>

This method can automatically manage the life cycle and prevent missed or missed resources.

Summarize

Although curl_multi_close is a necessary resource cleaning step, unreasonable or frequent calls will actually drag down system performance . By multiplexing multi handles , reasonably managing batch closure timing , or introducing connection pool management , the efficiency and stability of multi-request processing can be significantly improved.

In actual development, paying attention to these details will make your PHP application more comfortable when handling high concurrent HTTP requests.

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