[Opserty]

Work from the inside out...

1. [minicode]fetch_template()[/minicode] - fetches the template's HTML data (as a string) and returns it.
2. The concatanation appends the template data to the string, the [minicode]$navbar =...[/minicode]
3. Finally the [minicode]eval()[/minicode] evaluates the string as PHP code, so [minicode]$navbar[/minicode] becomes a proper variable instead of just a string. It will also mean that variables in the templates will assume their values assigned to them earlier in the script.

The start of this page shows the differences between single & double quotes and may help to explain why there are double quotes inside single quotes.

Its not hard to understand but if you are not well versed in PHP could take a while to explain it fully.