What specific data is received and processed in the CURLOPT_READFUNCTION callback function in PHP?

When using the CURLOPT_READFUNCTION callback function in PHP, the specific data received and processed is the data that needs to be sent in the request body when performing a POST request. This callback function allows you to provide a callback function that will be called to provide data to be uploaded. 

<?php

function read_callback($ch, $fd, $length)
{
    // Read data from a file handle ($fd) up to a certain length ($length)
    return fread($fd, $length);
}

$ch = curl_init();
$file_handle = fopen("data.txt", "r");

curl_setopt($ch, CURLOPT_URL, "http://example.com/api");
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_READFUNCTION, "read_callback");
curl_setopt($ch, CURLOPT_INFILE, $file_handle);

$response = curl_exec($ch);

fclose($file_handle);
curl_close($ch);

echo $response;

?>

Keywords

CURLOPT_READFUNCTION callback function data processing PHP data received

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