PHP function introduction—curl_multi_select(): Wait for the currently active cURL transfer to complete

PHP function introduction—curl_multi_select(): Wait for the currently active cURL transfer to complete

Introduction

In PHP, using the cURL library to make HTTP requests is a very common operation. When we need to handle multiple HTTP requests at the same time, we can use the curl_multi library to achieve this. When using the curl_multi library, we often need to wait for the currently active cURL transfer to complete. At this time, you can use the curl_multi_select() function.

Function definition

curl_multi_select(resource $mh[, float $timeout])

Parameter description

• $mh: cURL to wait for Batch handle.
• $timeout: Optional parameter, specify the waiting time limit. If set to 0, it returns immediately.

Function function

The curl_multi_select() function will wait for the currently active cURL transfer to complete and return the number of readable handles. Calling this function keeps our script active while waiting.

Example

$mh = curl_multi_init();

$ch1 = curl_init();
curl_setopt($ch1, CURLOPT_URL, "https://example.com/api/request1");
curl_setopt($ch1, CURLOPT_RETURNTRANSFER, true);
curl_multi_add_handle($mh, $ch1);

$ch2 = curl_init();
curl_setopt($ch2, CURLOPT_URL, "https://example.com/api/request2");
curl_setopt($ch2, CURLOPT_RETURNTRANSFER, true);
curl_multi_add_handle($mh, $ch2);

do {
    $status = curl_multi_exec($mh, $active);
    if ($active) {
        curl_multi_select($mh); // 等待当前活动的cURL传输完成
    }
} while ($active && $status == CURLM_OK);

// 处理完所有请求后，关闭cURL句柄
foreach ([$ch1, $ch2] as $ch) {
    curl_multi_remove_handle($mh, $ch);
    curl_close($ch);
}

curl_multi_close($mh);

In this example, we create a curl_multi handle and add two curl handles. We then use a loop to wait for the currently active cURL transfer to complete. In each loop, we call the curl_multi_exec() function to handle the cURL transfer and check whether there are any active transfers. If there is an active transfer, we call the curl_multi_select() function to wait and handle other tasks while waiting. The loop will run until all transfers are complete and there are no active transfers.

Finally, we close all cURL handles and curl_multi handles after processing all requests.

Summary

Using the curl_multi_select() function can help us wait for the currently active cURL transfer to complete. This keeps the script active while waiting, improving efficiency and performance of multiple HTTP requests.

Note: When using this function, please ensure that errors and exceptions have been handled correctly to prevent the script from falling into an infinite wait state.

The above is the detailed content of PHP function introduction—curl_multi_select(): Wait for the currently active cURL transfer to complete. For more information, please follow other related articles on the PHP Chinese website!