core-bundle/src/Resources/contao/library/Contao/Session.php
public function set($strKey, $varValue)
	{
		// Map the referer (see #281)
		if (\in_array($strKey, $this->mappedKeys))
		{
			$this->session->set($strKey, $varValue);
		}
		else
		{
			$this->sessionBag->set($strKey, $varValue);
		}
	}
public function set($strKey, $varValue)
	{
		// Map the referer (see #281)
		if (\in_array($strKey, $this->mappedKeys))
		{
			$this->session->set($strKey, $varValue);
		}
		else
		{
			$this->sessionBag->set($strKey, $varValue);
		}
	}
Set a session variable

@param string $strKey   The variable name
@param mixed  $varValue The variable value