Temuri,
Thank you for your kind words.
The reference in the manual is here https://docs.phalcon.io/en/latest/reference/volt.html
True most of the things you can do with Volt you can do it yourself with phtml files. However there are some that you cannot. For instance template inheritance (as I wrote), an easy way to render partials and also macros. The document section above lists all that.
Again it is ease of you and entirely up to the developer to use whatever they like. However for me personally:
this:
{% for row in data.projects.project %}
<div class="proj-item">
<h4><a href="/project/view/{{row.prj_id }}">{{ row.prj_name }}</a></h4>
<p>{{ row.prj_desc }}</p>
</div>
<hr/>
{% endfor %}
is easier to write and code than this:
<?php foreach ($data->projects->project as $row) { ?>
<div class="proj-item">
<h4><a href="/project/view/<?php echo $row->prj_id; ?>"><?php echo $row->prj_name; ?></a></h4>
<p><?php echo $row->prj_desc; ?></p>
</div>
<hr/>
<?php } ?>