The file extension and language is PHP, and need to highlight HTML and JavaScript at the same time with the main language PHP in Notepad++
Example of code to highlight:
<?php
$form_name = 'index';
?>
<!doctype html>
<html>
<head>
<script>alert('One = ' + 1);</script>
</head>
<body>
<input type="text" value="<?php $form_name; ?>">
</body>
</html>
Thank you