Fix stale getopt() optional value in CLI

Technically this applies to other SAPIs, but CLI is currently the only one with
a flag with an optional value. The PHP getopt() implementation already clears
php_optarg by-hand.

Fixes GH-21901
Closes GH-21902

Co-authored-by: Ilija Tovilo <ilija.tovilo@me.com>

Author: onthebed

NEWS

@@ -2,6 +2,9 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? ????, PHP 8.5.7
 
+- CLI:
+  . Fixed bug GH-21901 (Stale getopt() optional value). (onthebed)
+
 - Opcache:
   . Fixed tracing JIT crash when a VM interrupt is handled during an observed
     user function call. (Levi Morrison)

main/getopt.c

@@ -59,6 +59,9 @@ PHPAPI int php_getopt(int argc, char* const *argv, const opt_struct opts[], char
 	static char **prev_optarg = NULL;
 
 	php_optidx = -1;
+	if (optarg) {
+		*optarg = NULL;
+	}
 
 	if(prev_optarg && prev_optarg != optarg) {
 		/* reset the state */

sapi/cli/tests/gh21901.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Stale getopt() optional value in CLI
+--FILE--
+<?php
+$php_escaped = getenv('TEST_PHP_EXECUTABLE_ESCAPED');
+$cmd = $php_escaped . ' -n -d foo=bar --ini';
+echo shell_exec($cmd);
+?>
+--EXPECTF--
+Configuration File (php.ini) Path: "%S"
+Loaded Configuration File:         "%S"
+Scan for additional .ini files in: %s
+Additional .ini files parsed:      %s