Add PHP code ? Why ?
Imagine, you need a dynamic information on a static wevsite. For example, get something using an REST API.
Of course, it's possible to use javascript and an ajax resquest.
But, Fruga is written in PHP. PHP is "everywhere". It can be used directly in a webpage without an additional network request. The page will be static overall but a portion of it will call PHP.
Just add a php folder (name is free) in your template folder with a PHP file (for example helloword.php).
<?php
echo 'Hello World ' . date('d/m/Y');
?>
If you want this code on homepage, just edit themes/mytemplate/home.php then add at the desired location :
<?php
$page->addPHPCode('/php/helloword.php');
?>
In the output folder after generation, you'll have an index.php instead of index.html
(Sorry for the sometimes approximate English. If you want me to correct something, please contact me.)