Hello Gakanopd!

Yes, Dolphin (even the latest 7.3.5) version doesn't work with PHP 7.x, but need to be sure that your Dolphin inc/heder.inc.php is avalable. Also, please specify this situation: "I tried to update Dolphin to the latest version hoping that it would work " - so your server was upgraded to use PHP 7 and after this part you've tried to update your Dolphin? If there was another situation then please specify - did you Dolphin work after this upgrade?