Php file editor online

I have some code like this in my Index.php file

<?php include 'config.php'; ?>
<div class="center">
  <div class="col-lg-4 callout">
        <h3><?php echo $servicetitle1 ?></h3>
        <p><?php echo $servicedesc1 ?></p>
  </div>
</div>

and I had another file called config.php that contained the $ values such as

$servicetitle1  = "Title";
$servicedesc1   = "Description";

Could I in anyway have a 3rd php file that I could edit the values of the config.php file from, it would obviously be password protected. One up on that idea, Could I overlay a menu over index.php where I could edit the values directly?

All of this is for a client that would like "Easy" editing of his site. I know this is alot like WordPress and that is the way i am going without actually making a WordPress theme, Please also keep in mind that this applies to the whole page down to images but I'm sure that it can't be too hard to scale?