<?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.

namespace Facebook\WebDriver\Chrome;

use Facebook\WebDriver\Remote\Service\DriverService;

class ChromeDriverService extends DriverService
{
    // The environment variable storing the path to the chrome driver executable.
    const CHROME_DRIVER_EXE_PROPERTY = 'webdriver.chrome.driver';

    /**
     * @return static
     */
    public static function createDefaultService()
    {
        $exe = getenv(self::CHROME_DRIVER_EXE_PROPERTY);
        $port = 9515; // TODO: Get another port if the default port is used.
        $args = ["--port=$port"];
        $service = new static($exe, $port, $args);

        return $service;
    }
}

<?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.

namespace Facebook\WebDriver\Chrome;

use Facebook\WebDriver\Remote\Service\DriverService;

class ChromeDriverService extends DriverService
{
    /**
     * The environment variable storing the path to the chrome driver executable.
     * @deprecated Use ChromeDriverService::CHROME_DRIVER_EXECUTABLE
     */
    const CHROME_DRIVER_EXE_PROPERTY = 'webdriver.chrome.driver';
    // The environment variable storing the path to the chrome driver executable
    const CHROME_DRIVER_EXECUTABLE = 'WEBDRIVER_CHROME_DRIVER';

    /**
     * @return static
     */
    public static function createDefaultService()
    {
        $exe = getenv(self::CHROME_DRIVER_EXECUTABLE) ?: getenv(self::CHROME_DRIVER_EXE_PROPERTY);
        $port = 9515; // TODO: Get another port if the default port is used.
        $args = ['--port=' . $port];

        return new static($exe, $port, $args);
    }
}

Change variable name defining path to ChromeDriver executable
Change variable name defining path to ChromeDriver executable

1. Why is this change necessary?
Current environment variable in ChromeDriver.php uses '.', whilst valid according to the specification, this will not work using a bash shell (probably the most commonly used)

2. How does it address the issue?
'.' replaced with '_'.  This is usable in bash (including cygwin)
Original code still there, only attempts new variable if original does not exist

3. What are the side effects?
None, previous name will still work, new name only used if original name does not exist
