“Error: Undefined constant” after upgrading to PHP 8?

I’m getting this PHP error after upgrading to PHP 8:

Error: Undefined constant "Api​" in /home/xxxxxx/public_html/api-res/data.php:74

And the 74 line of data.php is this:

if ($State -> dbStruct && isset(Api_Db::$list[$State -> db])) {

$State -> dbStruct is a non-empty array, Api_Db::$list is a static array of class Api_Db, and $State -> db is a plain string of db name.

Tried to use absolute namespace ApiApi_Db but it didn’t work.

What’s wrong here? It’s really a weird error?

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When I switch back to PHP 7.2, it gives this error instead:

ErrorException: Use of undefined constant ​ - assumed '​' (this will throw an Error in a future version of PHP) in /home/datacty/public_html/api-res/data.php:74

What does this mean? There’s no constant in that line.