Yoast SEO 4.5: update your PHP version • Yoast

This is a rather special release, as it’s a project that’s close to my heart. It’s not a full-featured release, however, it is just necessary as a regular release. In Yoast SEO 4.5, we are urging site owners whose sites run on servers with an outdated version of PHP to update to a more recent version. To move the web forward, we need to take a stand against old, slow and unsafe software. Updating to PHP 7 will give your site an enormous speed boost. In this post, you’ll find out why we’re showing this notice in WordPress and what you can do to upgrade PHP. Why this move?
WordPress is built on PHP. This programming language takes care of the heavy lifting for the CMS. WordPress was always built with backward compatibility in mind, but we’ve reached a point where that’s just not feasible anymore. WordPress needs a minimum of PHP5.2 to function, but that version will not get updates, fixes or patches. This makes it inherently insecure. If you are on an old version, Yoast SEO 4.5 will show you a message in the backend. Please update to at least 5.6, but rather PHP 7 to take advantage of all the awesomeness of this new version. Not just for you as
Source: https://managewp.org/articles/14662/yoast-seo-4-5-update-your-php-version-yoast

source https://williechiu40.wordpress.com/2017/03/22/yoast-seo-4-5-update-your-php-version-%e2%80%a2-yoast/