json_decode() should generate a syntax error when given "".

Fixes bug #68938 (json_decode() decodes empty string without error).
Patch by jeremy at bat-country dot us.

NEWS

@@ -24,6 +24,10 @@ PHP                                                                        NEWS
   . Fixed bug #68571 (core dump when webserver close the socket).
     (redfoxli069 at gmail dot com, Laruence)
 
+- JSON:
+  . Fixed bug #68938 (json_decode() decodes empty string without error).
+    (jeremy at bat-country dot us)
+
 - Libxml:
   . Fixed bug #64938 (libxml_disable_entity_loader setting is shared
     between threads). (Martin Jansen)

ext/json/json.c

@@ -818,6 +818,7 @@ static PHP_FUNCTION(json_decode)
 	JSON_G(error_code) = 0;
 
 	if (!str_len) {
+		JSON_G(error_code) = PHP_JSON_ERROR_SYNTAX;
 		RETURN_NULL();
 	}
 

ext/json/tests/bug54484.phpt

@@ -15,11 +15,16 @@ json_decode("invalid json");
 var_dump(json_last_error());
 
 
+json_decode("\001 invalid json");
+var_dump(json_last_error());
+
+
 json_decode("");
 var_dump(json_last_error());
 ?>
 --EXPECT--
 int(0)
-int(0)
 int(4)
-int(0)
+int(4)
+int(3)
+int(4)

ext/json/tests/bug68938.phpt

@@ -0,0 +1,11 @@
+--TEST--
+Bug #68938 (json_decode() decodes empty string without indicating error)
+--SKIPIF--
+<?php if (!extension_loaded("json")) print "skip"; ?>
+--FILE--
+<?php
+json_decode("");
+var_dump(json_last_error());
+?>
+--EXPECT--
+int(4)