PHP 7 To PHP 8 Issue

[BulliM]

Since quite a while I get php 7.3 warnings in Nginx error.log:

FastCGI sent in stderr: "PHP message: PHP Warning: Use of undefined constant assets - assumed 'assets' (this will throw an Error in a future version of PHP) in /var/www/*******/includes/vb5/template.php(404) : eval()'d code on line 256

As long as it works I ignored that. But when I update PHP to version 8, the sub site is no longer available. Seems that warning occurs an error now.

In my code I cannot find any error. The problem seems to result in a loop of my (simplified) code:

PHP Code:

foreach($variables as $variable)
{
    $item = vB::getDbAssertor()->getRow('APINAME:TABLENAME', array('FIELDNAME' => $variable));
    $var[$i]['FIELD'][$y] = $item['FIELD'];
} 


Don't really know, what php8 needs to work at this point. Has anyone an idea?