Upgrade to 3.7.5.and php 7.1

Hello,

I’ve upgraded a site on quark template to joomla 3.7.5 and php 7.1.
Can’t see the site nor the administrator page.
In both pages shows this error:
Warning: session_start(): Failed to read session data: user (path: /tmp) in /home/zr1t8vuc/public_html/pt/libraries/joomla/session/handler/native.php on line 260
Error displaying the error page: Application Instantiation Error: Failed to start the session

Thank you.

I’ve solved it.
In php options.
Thanks