So basically you need two php files. One to handle the main overview page, and a second one to handle the actual full article page.
Then what you're going to want to do is integrate with some type of database. MySQL tends to be the most common when working with PHP, simply because it's free (as is PHP) and they work well together. You would then create a table in the database of articles which includes all of the article information.
On the main overview page, your php file will fetch the articles from the database and print out their snippet descriptions.
On the actual article page, your php file will fetch the desired article from the database and print out the full article.
What you're asking for isn't very complex. One database. One table. One php file to view all. One php file to view an individual article. And then, behind the scenes, you're going to want yet a third php file for you to actually submit new articles into the database.
Do you use your own CMS? if yes, then you should make your own function that can handle that. Maybe you could follow the suggestions from @Dani. But if you use a CMS such as Joomla, feature like that is already available. In Joomla you can download Mini FrontPage extensions. It's free.