Like every web programming languages, PHP also having it's unique syntax.
The process through which PHP parsing engine differentiate PHP code from other elements in a page called "Escaping to PHP".
There are diffrent ways as <?...?>, <%...%>, <script language="PHP">...</script>, <?php...?>
but always use <?php....?> tag as it is accepted universally and interpret your tag correctly. Moreover
if you use other tag then you will also need to edit your php.in file at server side.
Comments in PHP :-
Two forward slashes // are used for single line comment.
# is also used for single line comment.
/* ... */ is used for multiple-lines comments or to hide some part of line or