Thank you for the reply

In my main file I have the line return '@lammert_daservermonitor/lammert_da_servermonitor_side.php';
I have the file called "lammert_da_servermonitor_side.php" in the folder .\phpBB3\ext\lammert\daservermonitor\styles\Hexagon\template.

The code in the file:

{$LR_BLOCK ...

I also tried to use php and it gets commented out.
In the above example the line <?php echo "Hello"; ?> it gets commented and so it doesn't produce the "Hello" message, but only "Hi" that is printed with html code.
Did I miss something?