Headers functions do nothing in CLI SAPI

Description

It seems an stupid issue, but please read.
Related to #12303
The following code:

<?php
header('Custom: xxx');
print_r(headers_list());`

Resulted in this output:

Array
(
)

But I expected this output instead:

Array
(
    [0] => Custon: xxx
)

We know that the CLI SAPI don't send headers, and for that it's OK that the sapi_cli_send_headers() do nothing.
https://github.com/php/php-src/blob/master/sapi/cli/php_cli.c#L395-L405

But all the other header(), header_remove(), headers_list() that depend from sapi_cli_header_handler()
https://github.com/php/php-src/blob/master/sapi/cli/php_cli.c#L389-L392
can work normally from CLI using the fallback. Only the headers_sent() need to be always false.
https://github.com/php/php-src/blob/master/sapi/cli/php_cli.c#L446-L448

Related to #12303
https://3v4l.org/Wub2V

Actual behavior
https://3v4l.org/vZtmZ
Yes, it's curious that the setcookie() return true.
And the http_response_code() also work from CLI, we only need to set the initial value, but not the headers.

First because other php functions use it internally, like setcookie, session, ...

But it's more important to use php files without changes from CLI.
Basic example:

<?php
header_remove();
http_response_code(200);

ob_start();

include 'file.php';

$body = ob_get_clean();

$headers = create_status(http_response_code());

$headers .= implode("\r\n", headers_list()) . "\r\n";

$headers .= 'Content-Length: ' . strlen($body);

send_to_socket($headers, $body);

So we can use any PHP file from CLI and send it to any socket.
Actually we need to create custom functions to manage the headers, and change the normal php files.
But with the headers_list() and http_response_code() we can create all the http message.

BC: Nothing
That functions now do nothing from CLI.
If accepted it'll be good to be added to all php supported versions.

PHP Version

All

Operating System

All

Bắt đầu trong sapi/cli/php_cli.c, đặc biệt là sapi_cli_header_handler(), sapi_cli_send_headers() và phần triển khai headers_sent() được mô tả trong issue. Kiểm tra cách CLI hiện đang xử lý header(), header_remove(), headers_list(), http_response_code() và setcookie(). Được xem là hoàn tất khi CLI giữ lại trạng thái header cho các hàm này, vẫn không gửi header và headers_sent() vẫn là false; xác minh hành vi bằng các ví dụ PHP trong issue.