code: public static function extract($array, array $paths, $default = null) {
          $found = array();
          foreach ($paths as $path) {
              static::set_path($found, $path, static::path($array, $path, $default));
          }
  
          return $found;
      }
docs: Retrieves multiple paths from an array. If the path does not exist in the
  array, the default value will be added instead.
  
  // Get the values "username", "password" from $_POST
  $auth = Arr::extract($_POST, array('username', 'password'));
  
  // Get the value "level1.level2a" from $data
  $data = array('level1' => array('level2a' => 'value 1', 'level2b' => 'value 2'));
  Arr::extract($data, array('level1.level2a', 'password'));
  
  @param   array $array array to extract paths from
  @param   array $paths list of path
  @param   mixed $default default value
  @return  array