system/Session/Session.php
protected function setCookie()
	{
		setcookie(
				$this->sessionCookieName, session_id(), (empty($this->sessionExpiration) ? 0 : time() + $this->sessionExpiration), $this->cookiePath, $this->cookieDomain, $this->cookieSecure, true
		);
	}
protected function setCookie()
	{
		setcookie(
				$this->sessionCookieName, session_id(), (empty($this->sessionExpiration) ? 0 : time() + $this->sessionExpiration), $this->cookiePath, $this->cookieDomain, $this->cookieSecure, true
		);
	}
Takes care of setting the cookie on the client side.
Extracted for testing reasons.