Add json_decode flags for duplicate JSON object keys

NEWS

@@ -114,6 +114,8 @@ PHP                                                                        NEWS
 - JSON:
   . Enriched JSON last error / exception message with error location.
     (Juan Morales)
+  . Added JSON_DUPLICATE_KEY_MERGE and JSON_DUPLICATE_KEY_ARRAY flags to
+    json_decode() to control handling of duplicate object keys. (PurHur)
 
 - Fibers:
   . Fixed bug GH-20483 (ASAN stack overflow with fiber.stack_size INI small

UPGRADING

@@ -222,6 +222,8 @@ PHP 8.6 UPGRADE NOTES
 - JSON:
   . Added extra info about error location to the JSON error messages returned
     from json_last_error_msg() and JsonException message.
+  . Added JSON_DUPLICATE_KEY_MERGE and JSON_DUPLICATE_KEY_ARRAY flags to
+    json_decode() for duplicate object key handling.
 
 - OpenSSL:
   . Added TLS session resumption support for streams with new stream context

ext/json/json.c

@@ -322,6 +322,11 @@ PHP_FUNCTION(json_decode)
 		RETURN_THROWS();
 	}
 
+	if ((options & PHP_JSON_DUPLICATE_KEY_MERGE) && (options & PHP_JSON_DUPLICATE_KEY_ARRAY)) {
+		zend_argument_value_error(4, "cannot combine JSON_DUPLICATE_KEY_MERGE and JSON_DUPLICATE_KEY_ARRAY");
+		RETURN_THROWS();
+	}
+
 	/* For BC reasons, the bool $assoc overrides the long $options bit for PHP_JSON_OBJECT_AS_ARRAY */
 	if (!assoc_null) {
 		if (assoc) {

ext/json/json.stub.php

@@ -90,6 +90,17 @@
  */
 const JSON_THROW_ON_ERROR = UNKNOWN;
 
+/**
+ * @var int
+ * @cvalue PHP_JSON_DUPLICATE_KEY_MERGE
+ */
+const JSON_DUPLICATE_KEY_MERGE = UNKNOWN;
+/**
+ * @var int
+ * @cvalue PHP_JSON_DUPLICATE_KEY_ARRAY
+ */
+const JSON_DUPLICATE_KEY_ARRAY = UNKNOWN;
+
 /**
  * @var int
  * @cvalue PHP_JSON_ERROR_NONE