[php-src] Issue #18850: PHP Warning: Constant already defined when processing multiple sources with __halt_compiler()

Issue: https://github.com/php/php-src/issues/18850 Author: ProgerXP ### Description Whenever PHP processes more then one __halt_compiler() statement in one session, it emits this cryptic warning: ``` PHP Warning: Constant already defined in ... ``` Note the empty constant name. There are several ways to trigger this. Here's one: ``` # echo '<?php __halt_compiler();' >inc.php # php -a php > include('inc.php'); php > include('inc.php'); PHP Warning: Constant already defined in /tmp/inc.php on line 1 ``` here's another: ``` # php -r "eval('?><?php __halt_compiler();'); eval('?><?php __halt_compiler();');" ``` ### PHP Version ```plain PHP 8.4.5 (cli) (built: Mar 12 2025 16:58:15) (NTS) Copyright (c) The PHP Group Zend Engine v4.4.5, Copyright (c) Zend Technologies ``` ### Operating System _No response_