What does Undefined index mean: SELENIUM HUB in Selenium with phpunit?

I am trying to use katalon with selenium with the export for phpunit (since selenium removed it) to do a user test and it is coming out to me that Undefined index: SELENIUM_HUB, could you tell me to laugh the same? I'm looking for and I can't find something to clarify how to solve. This the code with the error.I'm using wamp as a localhost and I don't know if it can be on that side the problem Thanks

  <?php
namespace Test;

use PHPUnit\Framework\TestCase;
use Facebook\WebDriver;
require_once('vendor/autoload.php');

class ProbandoLaPagTest extends TestCase
{
    /**
     * @var WebDriver\Remote\RemoteWebDriver
     */
    private $webDriver;

    /**
     * @var string
     */
    private $baseUrl;

    /**
     * init webdriver
     */
    public function setUp():void
    {
        $desiredCapabilities = WebDriver\Remote\DesiredCapabilities::chrome();
        $desiredCapabilities->setCapability('trustAllSSLCertificates', true);
        $this->webDriver = WebDriver\Remote\RemoteWebDriver::create(
            $_SERVER['SELENIUM_HUB'],
            $desiredCapabilities
        );
        $this->baseUrl = $_SERVER['SELENIUM_BASE_URL'];
    }

    /**
     * Method testProbandoLaPag
     * @test
     */
    public function testProbandoLaPag()
    {
        // open | http://turi/ | 
        $this->webDriver->get("http://turi/");
        // click | link=Contacto | 
        $this->webDriver->findElement(WebDriver\WebDriverBy::linkText("Contacto"))->click();
        // click | id=nombre | 
        $this->webDriver->findElement(WebDriver\WebDriverBy::id("nombre"))->click();
        // type | id=nombre | Ezequiel
        $this->webDriver->findElement(WebDriver\WebDriverBy::id("nombre"))->sendKeys("Ezequiel");
        // type | id=apellido | Ledesma
        $this->webDriver->findElement(WebDriver\WebDriverBy::id("apellido"))->sendKeys("Ledesma");
        // type | id=email | ezequiel.ledesma026@gmail.com
        $this->webDriver->findElement(WebDriver\WebDriverBy::id("email"))->sendKeys("ezequiel.ledesma026@gmail.com");
        // click | id=telefono | 
        $this->webDriver->findElement(WebDriver\WebDriverBy::id("telefono"))->click();
        // type | id=telefono | 47347866
        $this->webDriver->findElement(WebDriver\WebDriverBy::id("telefono"))->sendKeys("47347866");
        // click | id=mensaje | 
        $this->webDriver->findElement(WebDriver\WebDriverBy::id("mensaje"))->click();
        // type | id=mensaje | Se prueba escribiendo un mensaje 
        $this->webDriver->findElement(WebDriver\WebDriverBy::id("mensaje"))->sendKeys("Se prueba escribiendo un mensaje");
        // click | name=submit | 
        $this->webDriver->findElement(WebDriver\WebDriverBy::name("submit"))->click();
    }

    /**
     * Close the current window.
     */
    public function tearDown():void
    {
        $this->webDriver->close();
    }

    /**
     * @param WebDriver\Remote\RemoteWebElement $element
     *
     * @return WebDriver\WebDriverSelect
     * @throws WebDriver\Exception\UnexpectedTagNameException
     */
    private function getSelect(WebDriver\Remote\RemoteWebElement $element): WebDriver\WebDriverSelect
    {
        return new WebDriver\WebDriverSelect($element);
    }
}