I got the following error while installing MediaWiki 1.27 Alpha: "Your session data was lost! Check your php.ini and make sure session.save_path is set to an appropriate directory.". I don't face the same problem when I install the stable version i.e. Mediawiki 1.26.2.
When I install MediaWiki 1.26.2, it works fine:
When I install MediaWiki 1.27 alpha, it gives me an error: