You could try using a header system (Let me explain):
Basically, have a file called: header.php which contains all the content around the where the different pages will exist (so like index.php, about.php etc) and then on each page you can call the header.php. This meaning that if you wanted to change the links then you can do this easily by just changing the header.php file and it will change every single page that has included the header..
Another solution could be to create a function:
echo '<a href="link1.php">link 1</a>';
// include the links function
Just would like to add that this is a common approach for web development. Depending on the server side scripting language, the technique may be different. For example, if this site was developed in asp.net, you could use master pages.