It should work. The way php (which WordPress is built in) works, is like this.
Basically, you have a normal web page. You could have that in one file, or with php you can split it into separate files. Splitting it allows you to use the same header and footer, for example, and then change out the body. Which is a very over simplified way that WordPress themes work. But let’s move on. So you put your header content in header.php, footer content in footer.php and page content in page.php.
Your header content (for example) includes the opening body tag.
Your page content includes everything between the body tags.
Your footer content includes the closing body tag and additional footer info.
Still with me?
Header is like this:
<html>
<head>
<title>Title goes here</title>
</head>
<body>
Now within the page.php page there are two lines that include the header and the footer and whatever page content you want with the WordPress loop and function calls:
<?php include('header.php'); ?>
//Page content goes here
<?php include('footer.php'); ?>
Then the footer is:
</body>
</html>
When a visitor goes to your site, WordPress tells it to display content and use the page template. The page template “compiles” on the server, which draws the content of header.php and footer.php into the page.php. So at runtime page.php contains a full html page, which includes your header and footer content. So if you call scripts in your header, you would be able to access them because they will be present at page load.
I hope that makes sense. It’s not accurate by any means, but I was trying to explain the concept of how the server side php works. I wanted to fully explain it because the interlinked term you used is not necessarily correct. The full page content is compiled on the server, not just linked to (although it does seem that way at first glance, I will admit).
You might look for a plugin that would handle this for you, if you manually code it then you manually have to change it. If you use a good plugin you can use the WordPress interface to make changes to your slider, like content or sometimes colors or even controls.
If you are just getting started, I hope you have a local test environment and are not making these changes on your live server. If you do not have one, look into Xampp or Wamp if on Windows or Mamp if on a Mac. Those will be your testing environment where you can get better acquainted with php, they allow you to run the server side code on your local machine. You can also install a local copy of your WordPress install, which is recommended before making changes to your live site. Let’s say you make a mistake and don’t have a backup, now your site is broken and you have to figure out how to undo it. If it’s your local it’s not as big a deal since your live site still works (although with out your slider currently).
Anyway hope that helps. And if you’re new to php do a Google search for “Diving into PHP”. It’s a good video series on php by Envato. Also they have “WordPress for Designers” which I think walks you through setting up a slider in WordPress while showing you the basics of theme design and code.
