<?php
  /**
   * Copyright 2010-2013 Amazon.com, Inc. or its affiliates. All Rights Reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License").
   * You may not use this file except in compliance with the License.
   * A copy of the License is located at
   *
   * http://aws.amazon.com/apache2.0
   *
   * or in the "license" file accompanying this file. This file 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 Aws\Common;
  
  /**
   * Represents an enumerable set of values
   */
  abstract class Enum
  {
      /**
       * @var array A cache of all enum values to increase performance
       */
      protected static $cache = array();
  
      /**
       * Returns the names (or keys) of all of constants in the enum
       *
       * @return array
       */
      public static function keys()
      {
          return array_keys(static::values());
      }
  
      /**
       * Return the names and values of all the constants in the enum
       *
       * @return array
       */
      public static function values()
      {
          $class = get_called_class();
  
          if (!isset(self::$cache[$class])) {
              $reflected = new \ReflectionClass($class);
              self::$cache[$class] = $reflected->getConstants();
          }
  
          return self::$cache[$class];
      }
  }