Why are some commands not working in Selenium WebDriver?

Question

PHP

Faced such a problem, some commands in selenium webdriver on php do not work. I do everything by examples:

$webdriver->connect("firefox");                  //работает
$webdriver->get("http://google.com/");     //работает
$webDriver->findElement(WebDriverBy::id('signIn'));    //не работает
$webDriver->sendKeys('php-webdriver');                      //не работает

Tell me what's the problem?

Answer 1

Well, there is no element on google.com with id signIn .