Fix invalid PHP code example
Fix invalid PHP code example

The `samesite` config was added in PHP 7.3, so the `if` check was the wrong way round.
Prior to 7.3 `session_set_cookie_params` didn't accept an array so this would have resulted in an error (https://3v4l.org/YKFrE). Changed to separate parameters. There are no longer any errors (https://3v4l.org/C0nGT)
GoogleChromeLabs/samesite-examples