Failing that I'd personally go down the route of using something like Drupal, Joomla or Wordpress but this would obviously take some integration if a site is already in place but as you didn't provide any indication as to the status of the website then this seems like a reasonable suggestion if you're starting from scratch.
Other than that, you'd probably have to create a bespoke admin system which could be done using PHP to write to a MySQL database which the frontend would then pull from the database.
Sorry to be honest but I have no idea of the technicals. Would it be possible for you to point me to a website that uses a similar web model. I think I will be able to understand this better when I see it.
There's definitely demo's of how joomla and drupal work on their own websites. Wordpress is used mainly for blogs but some people do also use it for other purposes but obviously depends what the requirements of the site are. All these use PHP and MySQL for the functionality so a basic understanding of this is needed if you want to get in and modify the code and a decent understanding of HTML and CSS is required for modifying the look and feel.
Obviously for a bespoke application, you can do whatever you want given the right skills.