In what scenarios can the CURLOPT_WRITEFUNCTION callback function be useful in PHP CURL requests?

The CURLOPT_WRITEFUNCTION callback function in PHP CURL requests can be useful when you want to handle the response data dynamically as it is being received, rather than waiting for the entire response to be received before processing it. This can be particularly useful when dealing with large responses or streaming data, as it allows you to process the data in chunks as it arrives.

// Initialize CURL session
$ch = curl_init();

// Set the URL to fetch
curl_setopt($ch, CURLOPT_URL, 'http://example.com/api');

// Set the callback function to handle the response data
curl_setopt($ch, CURLOPT_WRITEFUNCTION, function($ch, $data) {
    // Process the data chunk as it is received
    echo $data;

    // Return the length of the data processed
    return strlen($data);
});

// Execute the request
curl_exec($ch);

// Close CURL session
curl_close($ch);