Fix Bug #54058, invalid utf-8 doesn't set json_encode() in all cases

ext/json/json.c

@@ -538,7 +538,6 @@ static void json_encode_serializable_object(smart_str *buf, zval *val, int optio
 
 PHP_JSON_API void php_json_encode(smart_str *buf, zval *val, int options TSRMLS_DC) /* {{{ */
 {
-	JSON_G(error_code) = PHP_JSON_ERROR_NONE;
 	switch (Z_TYPE_P(val))
 	{
 		case IS_NULL:
@@ -680,6 +679,8 @@ static PHP_FUNCTION(json_encode)
 		return;
 	}
 
+	JSON_G(error_code) = PHP_JSON_ERROR_NONE;
+
 	php_json_encode(&buf, parameter, options TSRMLS_CC);
 
 	ZVAL_STRINGL(return_value, buf.c, buf.len, 1);

ext/json/tests/bug54058.phpt

@@ -0,0 +1,35 @@
+--TEST--
+Bug #54058 (json_last_error() invalid UTF-8 produces wrong error)
+--SKIPIF--
+<?php if (!extension_loaded("json")) print "skip"; ?>
+--FILE--
+<?php
+
+$bad_utf8 = quoted_printable_decode('=B0');
+
+json_encode($bad_utf8);
+var_dump(json_last_error());
+
+$a = new stdclass;
+$a->foo = quoted_printable_decode('=B0');
+json_encode($a);
+var_dump(json_last_error());
+
+$b = new stdclass;
+$b->foo = $bad_utf8;
+$b->bar = 1;
+json_encode($b);
+var_dump(json_last_error());
+
+$c = array(
+    'foo' => $bad_utf8,
+    'bar' => 1
+);
+json_encode($c);
+var_dump(json_last_error());
+?>
+--EXPECTF--
+int(5)
+int(5)
+int(5)
+int(5)