Selenium与PHP返回错误消息

I am attempting to set up selenium with php to run basic automation programs. So far I have downloaded selenium and gecko driver. Selenium is located at localhost:4444. All my selenium files have come from the following link: https://code.google.com/archive/p/php-webdriver-bindings/ and are saved in a htdocs folder within my MAMP.

Here is my code:

<?php


 require_once "phpwebdriver/WebDriver.php";


 $webdriver = new WebDriver("localhost", "4444");
 $webdriver->connect("firefox");
 $webdriver->get("http://google.com");
 $element = $webdriver->findElementBy(LocatorStrategy::name, "q");
 $element->sendKeys(array("selenium google code" ) );
 $element->submit();

 $webdriver->close();

?>

When I run this through my localhost:8888, it returns:

stdClass Object ( [sessionId] => [value] => stdClass Object ( [error] => invalid session id [message] => No active session with ID [stacktrace] => ) [status] => 6 )

Any help would be so greatly appreciated! Thanks!