<?php
// Copyright 2004-present Facebook. 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.
// 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.

abstract class WebDriverSingleKeyAction
    extends WebDriverKeysRelatedAction
    implements WebDriverAction {

  private $keys;

  public function __construct(
      WebDriverKeyboard $keyboard,
      WebDriverMouse $mouse,
      WebDriverLocatable $location_provider = null,
      $key = null) {
    parent::__construct($keyboard, $mouse, $location_provider);
    $this->key = $key;
  }
}

<?php
// Copyright 2004-present Facebook. 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.
// 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.

abstract class WebDriverSingleKeyAction
    extends WebDriverKeysRelatedAction
    implements WebDriverAction {

  protected $key;

  public function __construct(
      WebDriverKeyboard $keyboard,
      WebDriverMouse $mouse,
      WebDriverLocatable $location_provider = null,
      $key = null) {
    parent::__construct($keyboard, $mouse, $location_provider);
    $this->key = $key;
  }
}

Fix private property name and visibility
Fix private property name and visibility
