Respond early to a PHP request and keep processing

RespondEarly.php

<?php

// Provide a success response early
// Modified from: https://stackoverflow.com/a/42245266
function respondEarly() {
    if(session_id()) {session_write_close();}

    if(is_callable('fastcgi_finish_request')) {
        fastcgi_finish_request();
        return;
    }

    ignore_user_abort(true);
    ob_start();
    $serverProtocol = filter_input(INPUT_SERVER, 'SERVER_PROTOCOL', FILTER_SANITIZE_STRING);
    header($serverProtocol . ' 200 OK');
    header('Content-Encoding: none');
    header('Content-Length: ' . ob_get_length());
    header('Connection: close');
    ob_end_flush();
    flush();
}