Smarty

It seems to me that coding a test could designate a distinct compile and cache directory for each store. Much the same as I imagine you are distinguishing the database to use based on the Server Host ...

Nothing of what you describe is correct.
Don't run multiple sites within the same PHP pool.
Don't run multiple sites with shared cache.
Don't… basically, don't be that stupid. What you propose is ...

I plan to host many internet shops having on my webserver one set of PHP files, one Smarty installation, one templates folder and multiple mySQL databases - one database per internet shop. When a visi ...

That worked, thank you!

I have an array:

$activity = array("name" => "Challenge", "start-date" => "2019/02/14");

In order to output this variable, in the TPL file I put:
...