core-bundle/src/Resources/contao/library/Contao/Session.php
public function get($strKey)
	{
		// Map the referer (see #281)
		if (\in_array($strKey, $this->mappedKeys))
		{
			return $this->session->get($strKey);
		}

		return $this->sessionBag->get($strKey);
	}
public function get($strKey)
	{
		// Map the referer (see #281)
		if (\in_array($strKey, $this->mappedKeys))
		{
			return $this->session->get($strKey);
		}

		return $this->sessionBag->get($strKey);
	}
Return a session variable

@param string $strKey The variable name

@return mixed The variable value