Comment modes behavior in HTML and PHP

["C.R.Vegelin" <cr.vegelin@xxxxxxxxx>]

I have a PHP script, as follows:
<!--
   <?php
       echo "should this be echoed ?";
   ?>
-->

As expected, the browser shows nothing,
but when I view Source in the browser, I see:
<!-- start HTML comment
 should this be echoed ?-->

Shouldn't it be just: <!--  -->, without the echo result ?
I don't expect PHP to be active between <!--     -->.

TIA, Cor