Fixed bug #71731

The read_dimension() handler in BP_VAR_IS mode will now call
offsetExists() before caling offsetGet(). This has always been a
problem, however recently the issue has been exacerbated, because
the null-coalesce operator ?? makes it visible for non-nested
array accesses.

Also fixes #69659.

3 files changed, 81 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index d97e7c5a80..0cccc6abe7 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,9 @@ PHP                                                                        NEWS
   . Fixed Bug #71859 (zend_objects_store_call_destructors operates on realloced
     memory, crashing). (Laruence)
   . Fixed bug #71841 (EG(error_zval) is not handled well). (Laruence)
+  . Fixed bug #71731 (Null coalescing operator and ArrayAccess). (Nikita)
+  . Fixed bug #69659 (ArrayAccess, isset() and the offsetExists method).
+    (Nikita)
 
 - ODBC:
   . Fixed bug #63171 (Script hangs after max_execution_time). (Remi)
diff --git a/Zend/tests/bug71731.phpt b/Zend/tests/bug71731.phpt
new file mode 100644
index 0000000000..46a79f1a34
--- /dev/null
+++ b/Zend/tests/bug71731.phpt
@@ -0,0 +1,64 @@
+--TEST--
+Bug #71731: Null coalescing operator and ArrayAccess
+--FILE--
+<?php
+
+class AA implements ArrayAccess {
+    private $data = [];
+    public function offsetExists($name) {
+        echo "offsetExists($name)\n";
+        return array_key_exists($name, $this->data);
+    }
+    public function &offsetGet($name) {
+        echo "offsetGet($name)\n";
+        if (!array_key_exists($name, $this->data)) {
+            throw new Exception('Unknown offset');
+        }
+        return $this->data[$name];
+    }
+    public function offsetSet($name, $value) {
+        echo "offsetSet($name)\n";
+        $this->data[$name] = $value;
+    }
+    public function offsetUnset($name) {
+        echo "offsetUnset($name)\n";
+        unset($this->data[$name]);
+    }
+}
+
+$aa = new AA;
+var_dump(isset($aa[0][1][2]));
+var_dump(isset($aa[0]->foo));
+var_dump($aa[0] ?? 42);
+var_dump($aa[0][1][2] ?? 42);
+
+$aa[0] = new AA;
+$aa[0][1] = new AA;
+var_dump(isset($aa[0][1][2]));
+var_dump($aa[0][1][2] ?? 42);
+
+?>
+--EXPECT--
+offsetExists(0)
+bool(false)
+offsetExists(0)
+bool(false)
+offsetExists(0)
+int(42)
+offsetExists(0)
+int(42)
+offsetSet(0)
+offsetGet(0)
+offsetSet(1)
+offsetExists(0)
+offsetGet(0)
+offsetExists(1)
+offsetGet(1)
+offsetExists(2)
+bool(false)
+offsetExists(0)
+offsetGet(0)
+offsetExists(1)
+offsetGet(1)
+offsetExists(2)
+int(42)
diff --git a/Zend/zend_object_handlers.c b/Zend/zend_object_handlers.c
index 091a0a0d53..7b31fdc524 100644
--- a/Zend/zend_object_handlers.c
+++ b/Zend/zend_object_handlers.c
@@ -710,13 +710,26 @@ zval *zend_std_read_dimension(zval *object, zval *offset, int type, zval *rv) /*
 	zval tmp;
 
 	if (EXPECTED(instanceof_function_ex(ce, zend_ce_arrayaccess, 1) != 0)) {
-		if(offset == NULL) {
+		if (offset == NULL) {
 			/* [] construct */
 			ZVAL_NULL(&tmp);
 			offset = &tmp;
 		} else {
 			SEPARATE_ARG_IF_REF(offset);
 		}
+
+		if (type == BP_VAR_IS) {
+			zend_call_method_with_1_params(object, ce, NULL, "offsetexists", rv, offset);
+			if (UNEXPECTED(Z_ISUNDEF_P(rv))) {
+				return NULL;
+			}
+			if (!i_zend_is_true(rv)) {
+				zval_ptr_dtor(rv);
+				return &EG(uninitialized_zval);
+			}
+			zval_ptr_dtor(rv);
+		}
+
 		zend_call_method_with_1_params(object, ce, NULL, "offsetget", rv, offset);
 
 		zval_ptr_dtor(offset);