Exploring PHP Basics

WordPress requires PHP in order to work; therefore, your Web hosting

provider must have PHP enabled on your Web server. If you already have
WordPress up and running on your Web site, you know PHP is running and
working just fine. Currently, the PHP version required for WordPress is ver-
sion 4.3 or later.

In the very near future, WordPress will drop support for PHP version 4.
When this happens, version 5 will be the only version supported by the
WordPress platform. Ask your Web host to upgrade you to PHP version 5
sooner rather than later because most WordPress developers (for plugins,
themes, and so on) base their development practices on PHP version 5.