PHP is used to build most of the websites you see on Internet. Wordpress for example uses PHP to work, and that makes websites work and display pictures and information to you. PHP is far more complex than HTML and needs to be properly configured on each server. There are many versions of PHP, old ones are still used to support older websites, while new PHP versions are faster but less compatibile. The most common used is 5.4, that is rather old but still the standard setting on hosting providers.
On our server we have installed all versions of PHP, from 5.2 to 7.2. Trough your cPanel you can easily switch between all the PHP version and see if your website works with the latest and fasted version of PHP. If not you can switch down, until you find the version that works. We can assist you in making your website compatibile to PHP 7.2 to be able to get the maximum loading speed for your web pages.