xxxxxxxxxx
<?php
$param = "test";
?>
<a href="http://www.whatever.com/<?php echo $param; ?>">Click Here</a>
xxxxxxxxxx
<!-- you can put php code in html -->
<!DOCTYPE html>
<html>
<head>
<title>Hello</title>
</head>
<body>
<?php
//PHP code
?>
</body>
</html>