file_get_contents should probably clear the global state of last headers

Description

The following code:

<?php

file_get_contents(__FILE__);
var_dump(http_get_last_response_headers());

file_get_contents('https://php.net/');
var_dump(http_get_last_response_headers());

file_get_contents(__FILE__);
var_dump(http_get_last_response_headers());

Resulted in this output:

NULL
array( headers from php.net )
array( headers from php.net )

But I expected this output instead:

NULL
array( headers from php.net )
NULL // as reading a file clearly outputs no headers

IMO this is very surprising, and can lead to bugs (see https://github.com/jsonrainbow/json-schema/pull/843 for example) as people are now nudged to switch to http_get_last_response_headers() by the deprecations.

The problem is that $http_response_headers, while a very ugly API, was a local variable.. and http_get_last_response_headers() while appearing cleaner stores global state and can thus leak data across boundaries if you do not call http_clear_last_response_headers() after fetching the headers.

Thus my suggestion would be that file_get_contents first clears the headers and then populates them if the stream wrapper in use has anything to populate.

/cc @Girgias as I know you were involved in the deprecation. And apologies if this was already discussed somewhere I didn't find.

PHP Version

All versions where `http_get_last_response_headers()` is available

Operating System

No response

Start by running the PHP reproduction in the issue and reading the implementations of file_get_contents(), http_get_last_response_headers(), and http_clear_last_response_headers(). Trace how stream wrappers update the stored headers, then add coverage showing that a local-file read clears headers left by an earlier HTTP request; done means the final call returns NULL.