How to get current HTML source of AJAX page using facebook WebDriver?

Hi I am a facebook Webdriver newbie. I need help on getting HTML source of an AJAX page.

Here is my expected results:

$first == HTML source of the 1st page.
$second == HTML source of the 2nd page.

But my Output:

$first == HTML source of the 1st page.
$second == $first

However, I could get the HTML source of the 2nd page when I landed on the 3rd page. I don't know why I can not get the current HTML on Current page.

Please Help!

Here is my code (using selenium-server-standalone-2.44.0.jar):

$host = 'http://localhost:4444/wd/hub'; 
$capabilities = DesiredCapabilities::firefox();
$driver = RemoteWebDriver::create($host, $capabilities, 5000);

// Openning page
$driver->get('http://ift.tt/1wtsW1j');

// Click 'Search' 
$driver->findElement(WebDriverBy::className('yellow-submit'))->click();

// Wait until Ajax part loaded
$driver->wait(40)->until(
 WebDriverExpectedCondition::presenceOfAllElementsLocatedBy(
 WebDriverBy::className('actions-container')
));

// Print HTML of the 1st page
$first = $driver->getPageSource();
print_r($first);

// go to 2nd page
$driver->findElement(WebDriverBy::id('next'))->click();

// Wait until the 2nd page is loaded
$driver->wait(40)->until(
 WebDriverExpectedCondition::presenceOfAllElementsLocatedBy(
 WebDriverBy::className('actions-container')
));

// Print HTML of the 2nd page
$second = $driver->getPageSource();
print_r($second);

$driver->quit();