I can think of 2 possible solutions for you.
1. Dynamic with an include file.
2. Dynamic pulling from a SQL table.
The external include file would be easier to explain here, so I'll give you a quick example...
Add the following line to any page you want to include metatags to
<?php include ('my_metatags.php'); ?>
<?php echo MY_META; ?>
Create a file called my_metatags.php
Below are the contents that can be added to any and/or all pages on your website.
define('MY_META' , '<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="keywords" content="">
<meta name="description" content="">