diff --git a/php/Constants.php b/php/Constants.php
new file mode 100644
index 0000000..ef3730d
--- /dev/null
+++ b/php/Constants.php
@@ -0,0 +1,25 @@
+<?php
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+namespace Google\FlatBuffers;
+
+class Constants
+{
+    const SIZEOF_SHORT = 2;
+    const SIZEOF_INT = 4;
+    const FILE_IDENTIFIER_LENGTH = 4;
+}