如何在chrome扩展中执行PHP?

Hi I am trying to execute some php code in an extension so that it displays what you type into a form but when I run the extension it just displays the php file.

I've already tried executing the extension on "localhost/xampp" but I get the same results.

Popup.html:

<form action="test.php" method="post">
  <input name="object" type="text">
  <input type="submit">
</form> 

test.php:

<body>
<?php
echo $_POST["object"];
?>
</body>

I expect it to return what I type into the form but it displays the actual file.