I want to embed templates/info.html in templates/main_modern_layout.html

I have put <?php require 'templates/info.html';?> in templates/main_modern_layout.html , on the right column,
but nothing shows up?

how can I solve this?

Direct PHP code won't work in miniBB templates.

You will need to assign some PHP variable with the value and then put it into the table regular way like it happens with all other variables. For example, in your case, you might need to read the contents of the file

then put {$tplInfo} in templates/main_modern_layout.html.

Related thread.

Okay, I need to put this into templates/main_modern_layout.html:

{$tplInfo}

But where should I put this?? Should I put this into bb_plugins.php:

<?php
$tplInfo = "test";
?>

it works like charm!!!

Now I can use $tplInfo in all templates in templates folder, am I right?

MiniBB is great!!

This approach could be used for any template, any add-on as well.
Thanks, and have success while experimenting :)