PHP version 5.6 will no longer be supported by the end of 2018. PHP is one of the main programming codes behind WordPress (and many other website types of websites).
This means that the good people who maintain PHP will no longer be rolling out security updates. And consequently, plugin and theme developers will start to stop backwards compatability. Because of this, you may get a warning message that your ‘PHP is outdated’.
The good news is that you should be using PHP 7.2 because there are performance benefits for your website (ie. it will load faster).
To check what version of PHP you are currently using, you can use the Display PHP Version plugin from the WordPress plugin repository. Simply install the plugin, activate and it will show the PHP version on your dashboard.
You can use the PHP Compatability Checker plugin from the WordPress plugin repository to see if there will be any issues with updating your website PHP version.
Your web developer can set up a version of your website on a local server to simulate updating and sort out any issues before the update is done on the live site.
The actual updating of the PHP version can be done through your hosting by logging into your cPanel or Plesk dashboard.
Contact Webtree if you require any assistance with upgrading your PHP version.