From 440676a69a38bf3d847ba9b5627ded7de12e51b9 Mon Sep 17 00:00:00 2001
From: Ilija Tovilo <ilija.tovilo@me.com>
Date: Sat, 4 Dec 2021 22:35:57 +0100
Subject: [PATCH] Fix invalid opcode for ??= on $GLOBALS

Fixes #81684
---
 NEWS                     |  2 ++
 Zend/tests/bug81684.phpt | 11 +++++++++++
 Zend/zend_compile.c      |  4 +++-
 3 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 Zend/tests/bug81684.phpt

diff --git a/NEWS b/NEWS
index 64d41569809e..f1ef2bd35efe 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,8 @@ PHP                                                                        NEWS
 
 - Core:
   . Fixed bug #81216 (Nullsafe operator leaks dynamic property name). (Dmitry)
+  . Fixed bug #81684 (Using null coalesce assignment with $GLOBALS["x"] produces
+    opcode error). (ilutov)
 
 - MBString:
   . Fixed bug #81693 (mb_check_encoding(7bit) segfaults). (cmb)
diff --git a/Zend/tests/bug81684.phpt b/Zend/tests/bug81684.phpt
new file mode 100644
index 000000000000..e47056187a76
--- /dev/null
+++ b/Zend/tests/bug81684.phpt
@@ -0,0 +1,11 @@
+--TEST--
+Bug #81684: ??= on $GLOBALS produces an invalid opcode
+--FILE--
+<?php
+$GLOBALS['x'] ??= 'x'; // Fatal error: Invalid opcode 23/1/0
+var_dump($GLOBALS['x']);
+echo "Done.\n";
+?>
+--EXPECT--
+string(1) "x"
+Done.
diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c
index 63fb6314c1a7..c136d226e3c2 100644
--- a/Zend/zend_compile.c
+++ b/Zend/zend_compile.c
@@ -8986,7 +8986,9 @@ static void zend_compile_assign_coalesce(znode *result, zend_ast *ast) /* {{{ */
 
 	/* Reproduce some of the zend_compile_assign() opcode fixup logic here. */
 	opline = &CG(active_op_array)->opcodes[CG(active_op_array)->last-1];
-	switch (var_ast->kind) {
+	/* Treat $GLOBALS['x'] assignment like assignment to variable. */
+	zend_ast_kind kind = is_global_var_fetch(var_ast) ? ZEND_AST_VAR : var_ast->kind;
+	switch (kind) {
 		case ZEND_AST_VAR:
 			zend_emit_op_tmp(&assign_node, ZEND_ASSIGN, &var_node_w, &default_node);
 			break;