Autoload function for Google_* classes

Addresses googleapis#341

Author: ltrebing

autoload.php

@@ -0,0 +1,33 @@
+<?php
+/*
+ * Copyright 2014 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.
+ */
+
+function google_api_php_client_autoload($className) {
+  $classPath = explode('_', $className);
+  if ($classPath[0] != 'Google') {
+    return;
+  }
+  if (count($classPath) > 3) {
+    // Maximum class file path depth in this project is 3.
+    $classPath = array_slice($className, 0, 3);
+  }
+  $filePath = dirname(__FILE__) . '/src/' . implode('/', $classPath) . '.php';
+  if (file_exists($filePath)) {
+    require_once($filePath);
+  }
+}
+
+spl_autoload_register('google_api_php_client_autoload');