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Yes, you can do that. That is a good way to do it.
The only thing that would probably need to be changed on every page would be the description meta tag. I've seen Google use the meta description in its search results so it is worth having. Because every page is different, it is good to have a different description for each page.
Here is a way to make the meta description different on every page.
header.php
Code:
<html>
<head>
<title><?php echo $title; ?></title>
<meta name="description" content="<?php echo $description; ?>">
<meta name="keywords" content="<?php echo $keywords; ?>">
</head>
etc. etc.
index.php
Code:
<?php
$title = "My website!"
$description = "The unique description goes here.";
$keywords = "The unique keywords go here";
include("header.php");
?>
ect. etc.
Hope that helps