Upgrade to PHP 8.1 (#6711)

* Upgrade to PHP 8.1
As discussed in https://github.com/FreshRSS/FreshRSS/discussions/5474

https://www.php.net/releases/8.0/en.php
https://www.php.net/releases/8.1/en.php

Upgrade to available native type declarations
https://php.net/language.types.declarations

Upgrade to https://phpunit.de/announcements/phpunit-10.html which requires PHP 8.1+ (good timing, as version 9 was not maintained anymore)

Upgrade `:oldest` Docker dev image to oldest Alpine version supporting PHP 8.1: Alpine 3.16, which includes PHP 8.1.22.

* Include 6736
https://github.com/FreshRSS/FreshRSS/pull/6736

1 files changed, 1 insertions, 1 deletions

diff --git a/README.md b/README.md
index 093b94e40..38db3cfc3 100644
--- a/README.md
+++ b/README.md
@@ -62,7 +62,7 @@ FreshRSS comes with absolutely no warranty.
 * Light server running Linux or Windows
 	* It even works on Raspberry Pi 1 with response time under a second (tested with 150 feeds, 22k articles)
 * A web server: Apache2.4+ (recommended), nginx, lighttpd (not tested on others)
-* PHP 7.4+
+* PHP 8.1+
 	* Required extensions: [cURL](https://www.php.net/curl), [DOM](https://www.php.net/dom), [JSON](https://www.php.net/json), [XML](https://www.php.net/xml), [session](https://www.php.net/session), [ctype](https://www.php.net/ctype)
 	* Recommended extensions: [PDO_SQLite](https://www.php.net/pdo-sqlite) (for export/import), [GMP](https://www.php.net/gmp) (for API access on 32-bit platforms), [IDN](https://www.php.net/intl.idn) (for Internationalized Domain Names), [mbstring](https://www.php.net/mbstring) (for Unicode strings), [iconv](https://www.php.net/iconv) (for charset conversion), [ZIP](https://www.php.net/zip) (for import/export), [zlib](https://www.php.net/zlib) (for compressed feeds)
 	* Extension for database: [PDO_PGSQL](https://www.php.net/pdo-pgsql) or [PDO_SQLite](https://www.php.net/pdo-sqlite) or [PDO_MySQL](https://www.php.net/pdo-mysql)