Understanding and using the PHP scripting language allows you to use your WordPress software to even greater extent.
A great resource for beginners of PHP is Getting Started from The PHP Manual.
And here is a link to the first of a great series of YouTube videos on PHP
1: Introduction to PHP programming | PHP tutorial | Learn PHP programming 5:29 YouTube video. By mmtuts Published on Oct 19, 2015. Here is what the author says:
Introduction to PHP programming, is the first episode in this PHP tutorial for beginners series. This is a complete PHP tutorial for absolute beginners, teaches PHP to people who are new at it.
PHP is easy to learn and should not be made harder than it really is, and this is what I’m hoping to accomplish. In this lesson I will introduce the programming language called PHP and talk about the requirements of getting started on it. I will also give examples of what you can do with PHP.
2: Installing a local server for PHP | PHP tutorial | Learn PHP programming mmtuts
Published on Oct 20, 2015
Installing a local server – Learn backend programming. In this video we will learn how to install a local server on your computer.
Installing a local server is fast, easy, and doesn’t harm you computer in any way. To install a local server we will need to install a small software, and while there are many to choose from, I have chosen the one called XAMPP. XAMPP works on both PC, Mac, and Linux, and in order to avoid compatibility issues or errors with the server we are working on, I recommend that you use the same software we use in the tutorial.
Download XAMPP here: https://www.apachefriends.org/index.html
3: Output in browser using PHP | PHP tutorial | Learn PHP programming