PHP supports 'C','C++' and Unix shell-style (Perl style) comments.you can set single and multiple line comments in php the following example of php comments.
<?php
echo 'This is a test'; // This is a one-line c++ style comment
/* This is a multi line comment
yet another line of comment */
echo 'This is yet another test';
echo 'One Final Test'; # This is a one-line shell-style comment
?>