How to call PHP code

[michael]

How do I call from c#, PHP code that will print/echo to the screen (web
browser)?

For example

index.aspx
------------
<%
// code to call my_php_file.php
.....
%>

my_php_file.php
-----------------
<?php
echo "<h2>Hello world</h2>"
?>
RESULT
The web browser display in H2 tags "Hellow world"?

Thanks in advance