A web application is different from a desktop application. The web application like a dynamic website requires a unique environment called web server to work. To open the website, you also need a client program called web browser. Usually, people create and develop the website for the first time on the local web server on their personal computer before ready to move it to a web hosting server for online.
If you plan to create a website based on PHP web programming language and MySQL database on your computer, not on web hosting server, you need to have a local web server that consists of software such as Apache web server, PHP, MySQL, and also phpMyAdmin. You can get and download all software you need free from the internet, install them one by one on your computer and then configure them well to connect to each other.
For most people, configuring Apache web server, PHP, MySQL, and phpMyAdmin manually to connect to each other is not easy. It needs the skill and knowledge. Therefore, most people prefer to use a web solution package like a LAMP, XAMPP, WampServer, or AMPPS for ease of creating a local web server. You don't need to configure manually to use one of them. The configuration will be done automatically during the installation process.
The website such as a personal website, business website or portfolio website can be created from scratch using a web programming language such as PHP, Java, or Phyton. But nowadays, most people prefer to use Content Management System (CMS) for ease. A CMS like Joomla, Wordpress, or Drupal is good option to create an instant website. If you choose to use one of them, for example, Joomla CMS, you need to know the system requirements before using it. The latest version of Joomla requires specific system requirements to support its performance. One of them is the use of PHP version that is PHP 7.
If you create a local web server on your PC using WampServer, you can select to use the latest PHP version, for example, PHP 7.x or above. This is possible because, after the installation of WampServer completed, WampServer offers some PHP versions you can select to suit your web development needs. If your Joomla CMS requires a specific version of PHP, here's how to change the PHP version you want to use in Wampserver:
First, run WampServer, click the Show hidden icons button (1), and then click the local server button or button with the WampServer logo (2).
In the list of menus that appear, select PHP (1), next then select Version (2), and then select the latest version of PHP (3).