error Undefined offset: 1 selenium

Good afternoon, I'm having a bug in a selenium class. Does anyone know how to solve it? the code snippet is this.

 /* new way to retrieve sessionId from response in selenium 2.35.0 */
 list($headers, $content) = explode("\r\n\r\n", $rawResponse, 2);
 $jsonResponse = json_decode($content);
 $sessionId = $jsonResponse->{'sessionId'};
 $this->requestURL = $header['url'].'/'.$sessionId;
 //print_r($this->requestURL); 

Code I want to use

  require_once "phpwebdriver/WebDriver.php";
  $webdriver = new WebDriver("localhost", "4444");
  $webdriver->connect("firefox");                            
  $webdriver->get("http://google.com");
  $element = $webdriver->findElementBy(LocatorStrategy::name, "q");
  if ($element) {
  $element->sendKeys(array("php webdriver" ) );
  $element->submit();
  }
 $webdriver->close();

This code is 2013, I think with the selenium updates this part has become obsolete.

selenium ( link ). class documentation ( link ) ...