$driver = RemoteWebDriver::create($host, $capabilities);
// Execute Mozilla vendor-specific print command
$driver->executeCustomCommand(
    '/session/:sessionId/moz/print/', 
    'POST'
);
// Execute Mozilla vendor-specific full-page screenshot command
$screenshot = $driver->executeCustomCommand(
    '/session/:sessionId/moz/screenshot/full/',
    'POST'
);
file_put_contents('full.png', base64_decode($screenshot));
// Execute Appium command to get content of the system clipboard
$clipboard = $driver->executeCustomCommand(
    '/session/:sessionId/appium/device/get_clipboard/',
    'POST'
);
// Execute ChromeDevTools protocol command
$result = $driver->executeCustomCommand(
    '/session/:sessionId/goog/cdp/execute',
    'POST',
    ['cmd' => 'Runtime.evaluate', 'params' => ['expression' => 'window.location.toString()']]
);