PHP code is executed on the server, and the plain HTML result is sent to the browser. A PHP scripting block can be placed anywhere in the document. It always starts with <?php and ends with ?>.
The example of PHP code below sends the text “Google” to the browser:
<html>
<body>
<?php
echo " Google";
?>
</body>
</html>
To make a single-line comment, use //. To make a large comment block, use /* and */. See the example below:
<html>
<body>
<?php
//This is a comment
/*
This is
a comment
block
*/
?>
</body>
</html>
information is taken from the tutorial resource PHP Tutorials