PHP function introduction—curl_multi_init(): Initialize a multiple cURL session

PHP function introduction—curl_multi_init(): Initialize a session with multiple cURLs

Introduction:
In PHP, the curl_multi_init() function is used to initialize a session with multiple cURLs, which can be processed at the same time Multiple URL requests. This function creates a new curl_multi handle and returns a resource handle. In this session, we can add multiple cURL handles and execute them to achieve the purpose of processing multiple URLs at the same time.

Syntax:
resource curl_multi_init(void)

Return value:
If successful, return the session handle, if failed, return FALSE.

Code example:
The following is a simple example code that shows how to use the curl_multi_init() function to initialize a multiple cURL session and handle two URL requests at the same time.

<?php
// 初始化会话
$mh = curl_multi_init();

// 创建URL列表
$urls = array(
    'http://www.example.com/url1',
    'http://www.example.com/url2'
);

// 创建cURL句柄并添加到会话
$handles = array();
foreach ($urls as $url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_multi_add_handle($mh, $ch);
    $handles[] = $ch;
}

// 执行会话中的cURL句柄
$active = null;
do {
    $result = curl_multi_exec($mh, $active);
} while ($result == CURLM_CALL_MULTI_PERFORM || $active);

// 处理结果
foreach ($handles as $handle) {
    $response = curl_multi_getcontent($handle);
    // 处理响应数据
    echo $response;
    
    // 移除句柄和关闭cURL
    curl_multi_remove_handle($mh, $handle);
    curl_close($handle);
}

// 关闭会话
curl_multi_close($mh);
?>

Analysis:
In the above example code, a session is first initialized using the curl_multi_init() function, and then a URL list is created. Next, a foreach loop is used to traverse the URL list, and multiple cURL handles are created using the curl_init() function. The CURLOPT_RETURNTRANSFER option is set so that response data is returned. Then use the curl_multi_add_handle() function to add each handle to the session and save the handles to the $handles array.

After that, use the curl_multi_exec() function to execute all handles in the session at the same time. Get the return value $result and the number of active handles $active, and determine whether execution needs to continue in the do-while loop.

After the loop ends, use the curl_multi_getcontent() function to obtain the response data of each handle and process it. Then use the curl_multi_remove_handle() function to remove the handle from the session, and use the curl_close() function to close each cURL handle.

Finally, use the curl_multi_close() function to close the session.

Summary:
By using the curl_multi_init() function, we can easily initialize a multiple cURL session and implement the function of processing multiple URL requests at the same time. This is useful when you need to request multiple APIs or download multiple files at the same time. Using the curl_multi_init() function can improve the efficiency and response speed of the program.

So, learning and mastering the curl_multi_init() function and other related cURL functions can give you a deeper understanding and application of PHP's network request function.

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