We actually have a blog post for this exact question. https://paragonie.com/blog/2016/04/go-php-7-our-commitment-maintaining-our-open-source-projects https://p

We actually have a blog post for this exact question. https://paragonie.com/blog/2016/04/go-php-7-our-commitment-maintaining-our-open-source-projects https://paragonie.com/blog/2016/04/go-php-7-our-commitment-m... The short of it: * PHP 7 allowed us a combination of type safety and brevity that makes it much easier to reason about the security of Halite in a way that PHP 5 does not. * There is a very bad habit in the PHP community, led by WordPress, to provide very legacy support (i.e. PHP 5.2.4 in 2016). For that reason, we're going against the grain focusing on PHP 7 only. If people want to use any of our new open source libraries, they need to make the decision to upgrade now.