PHP script not working in HTML file
I'm new to PHP. I installed XAMPP and have Apache running. I created helloworld.php in XAMPP's htdocs and got PHP to display in my browser. My question is, why does my PHP script in my HTML file not display in my browser? Ive never installed PHP on its own. Should I also install it? Would it conflict with XAMPP. My code is below. Any assistance will be appreciated. Thanks in advance:  

    <html>
<body>

<?php
echo "Hello PHP World";
?>

</body>
</html>
PHP script not working in HTML file
===

I'm new to PHP. I installed XAMPP and have Apache running. I created helloworld.php in XAMPP's htdocs and got PHP to display in my browser. My question is, why does my PHP script in my HTML file not display in my browser? Ive never installed PHP on its own. Should I also install it? Would it conflict with XAMPP. My code is below. Any assistance will be appreciated. Thanks in advance:  

    <html>
<body>

<?php
echo "Hello PHP World";
?>

</body>
</html>