Description:
------------
Running under mod_php, calling

    header('HTTP/1.1 200 OK');

seems to prevent the connection from being closed once the PHP script finishes. This can be demonstrated by, for instance, hitting the script with ab (the Apache benchmark tool), which (unlike most HTTP clients, including browsers) only considers a request to have finished once the connection is closed, rather than when Content-Length bytes have been received. http://stackoverflow.com/q/34367115/1709587 describes this case in more detail.

Bizarrely,

    header('http/1.1 200 OK');

does not have the same effect, despite producing a character-for-character identical HTTP response (as can be observed with `curl -i --raw`).

Test script:
---------------
<?php

header('HTTP/1.1 200 OK');


Expected result:
----------------
Unless `Connection: keep-alive` is specified in the request, the connection should close once the PHP script finishes. In particular, the behaviour should be identical to other calls with the same meaning, like

    <?php
    
        http_response_code(200);

or

    <?php

        header('http/1.1 200 OK')

Actual result:
--------------
The connection does not close, and the alternate scripts suggested above have different behaviours to the test script.