I have a web page that has 3 files named header.php, footer.php, and index.php.. Header has the top logo and the side navigation. Footer has the bottom of the website, and index has the content. How do I put whatever I want into the index.php? Here is the coding I have for index.php

Code:
<html>
<head>
<title>blahblahtitle>
</head>

<body bgcolor="#000000">
<? 
include 'header.php'; 


echo "i want the content to go here"; 
      
include 'footer.php'; 
?> 

</body>
</html>