PHP supports 'C', 'C++' and Unix shell-style (Perl style) comments. For example:
<?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
?>
The "one-line" comment styles only comment to the end of
the line or the current block of PHP code, whichever comes first.
This means that HTML code after // ... ?>
or # ... ?> WILL be printed:
?> breaks out of PHP mode and returns to HTML mode, and
// or # cannot influence that.
<h1>This is an <?php # echo 'simple';?> example</h1>
<p>The header above will say 'This is an example'.</p>
'C' style comments end at the first */ encountered.
Make sure you don't nest 'C' style comments. It is easy to make this
mistake if you are trying to comment out a large block of code.
<?php
/*
echo 'This is a test'; /* This comment will cause a problem */
*/
?>