WordPress "Expect" header fix

expect-header-fix.php

<?php

/**
 * By default, cURL sends the "Expect" header all the time which severely impacts
 * performance. Instead, we'll send it if the body is larger than 1 mb like
 * Guzzle does.
 */
function add_expect_header(array $arguments)
{
    $arguments['headers']['expect'] = !empty($arguments['body']) && strlen($arguments['body']) > 1048576 ? '100-Continue' : '';
    
    return $arguments;
}
add_filter('http_request_args', 'add_expect_header');