Even though the recommendations have been updated to:
To run WordPress we recommend your host supports:
- PHP version 5.6 or greater
- MySQL version 5.6 or greater OR MariaDB version 10.0 or greater
the minimum requirements are not there yet:
WordPress server requirements for Version 3.2+:
- PHP version 5.2.4 or greater
- MySQL version 5.0.15 or greater or any version of MariaDB
Note that older versions of MySQL and PHP may have reached End Of
Life, which means they are no longer updated and can expose your site
to security vulnerabilities. For this reason, it’s best to follow the
recommended setup below and use the latest versions of MySQL/MariaDB
and PHP that your host supports.
The reason for this is e.g.:
Why do we support older versions? We strongly recommend the latest
versions of PHP and MySQL, but we understand that this isn’t right for
everyone, and that sometimes hosts can be slow or hesitant to upgrade
their customers since upgrades to PHP and MySQL have historically
broken applications.
Hopefully the WordPress core will apply all these handy things like generators (PHP 5.5+) and namespaces (PHP 5.3+) but it will take time.
Here’s e.g. a discusssion in #36335 regarding autoloading with support for PHP 5.2+.
WordPress core also runs fine on PHP 7.
But we can of course use these PHP improvements in our own projects and many plugins are not following the minimum requirements, thankfully 😉