[php-src] Issue #20406: Date parser does'nt speak ISO weekdates

Issue: https://github.com/php/php-src/issues/20406 Author: hgshoggins ### Description The following code: ```php <?php $dateTimeObj_monday = new DateTimeImmutable('2022W1', new DateTimeZone('Europe/Paris')); ``` Resulted in this output: ``` PHP Fatal error: Uncaught DateMalformedStringException: Failed to parse time string (2022W1) at position 5 (1): Unexpected character in test.php:7 Stack trace: #0 /root/test.php(7): DateTimeImmutable->__construct() ``` But I expected this output instead: a correctly set DateTimeImmutable object. It seems that the parser refuses to recognize the "W" for week specification. ### PHP Version ```plain PHP 8.4.14 (cli) (built: Oct 21 2025 19:23:55) (NTS gcc x86_64) Copyright (c) The PHP Group Built by Fedora Project Zend Engine v4.4.14, Copyright (c) Zend Technologies ``` ### Operating System Fedora 42