You can view html in any text editor's html preview, but for php you'll need a server.
Not entirely true. There's a few pretty nifty applications out there useful for developing PHP. A favourite one of mine is called "EasyPHP" - it's dirt simple and allows you to execute PHP scripts on your local machine.
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As a solution, I'm going to give you a simple example of Swanny's suggestion, as for someone of your experience it's an excellent starting point (and is pretty similar to what the dude who got me started in this had me do as a first script come to think of it)
Before I begin this, I'll just give an honorable mention to how every coder learns how to do something new in a language. We Google "PHP <<PROBLEM>>".
So, say I didn't know how to list files in a directory in PHP, I would Google "PHP list files in directory" - and chances are one of the top 5 results is a Webmaster World or Stack Overflow page with someone who once wanted to do exactly the same thing you did - with a helpful solution or link to a solution below.
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Anyway... we'll assume you have no solution currently implemented. The first step is to create a plain text file called ".htaccess" in the root directory of our site.
.htaccessAddType application/x-httpd-php5 .php .html
Now PHP code can be written into .html files and will execute as PHP rather than print as text.
Now we'll move on to actually converting the pages. First up is a totally legitmate copy of your about us page, which for the sake of argument, you have saved in wwwroot/pages/:
about_us.html<!DOCTYPE html>
<html>
<head>
<title>Boyd's Toast :: About Us</title>
</head>
<body>
<h1>Boyd's Toast</h1>
<p class="small">The best toast on the East coast</p>
<hr>
<h2>About Us</h2>
<p>We make the best toast ever.</p>
<p><strong>Ever.</strong></p>
<hr>
Copyright © Boyd's Toast
</body>
</html>
There's 2 segments of that file which can pretty easily be pulled out into seperate files.
So. Let's create these 2 new files:
header.php<!DOCTYPE html>
<html>
<head>
<title>Boyd's Toast :: <?php echo $pageTitle; ?></title>
</head>
<body>
<h1>Boyd's Toast</h1>
<p class="small">The best toast on the East coast</p>
<hr>
<h2><?php echo $pageTitle; ?></h2>
footer.php<hr>
Copyright © Boyd's Toast
</body>
</html>
And we'll save these 2 files in wwwroot/include/
We've now created 2 files that contain the common elements of all our pages. Now we need to modify about_us.html to make use of them. There are 2 ways of doing this, using either php's require method, or php's include method. They're very similar in use (just change require for include or vice versa) but they behave a bit differently.
Include - if it fails to locate the file, will log a warning, and allow the script to continue.
Require - if it fails to locate the file, will log a fatal error and cease further script execution.
I personally favour require, as I know I have the file then.
You'll also notice that in header.php I am echo (an equivilent to "print" in PHP) 'ing $pageTitle. This is a variable in PHP, so before including header.php, I will need to initialise this variable.
So, with all that in mind, we can rebuild about us, to this:
NEW about_us.html<?php
$pageTitle = 'About Us';
require '../include/header.php';
?>
<p>We make the best toast ever.</p>
<p><strong>Ever.</strong></p>
<?php
require '../include/footer.php';
?>
A further note on require / include:
Not preceeding the file path with a forward slash, as in the above example, will cause PHP to look for the included file in relation to the current file (what is called a relative path)
Preceeding the file path with a forward slash will cause PHP to look for the included file relative to the server root (note site root - important distinction) - this is called an absolute path.
