If you haven't been working with PHP lately, you might wonder what happened to PHP 6. Why the skip from PHP 5 to PHP 7? Well, long story short, PHP 6 was a failure. To avoid confusion, the new version was renamed PHP 7.
PHP 7 introduces a number of new features, while at the same time dropping depreciated SAPIs and extensions. As a result, it tends to outperform PHP 5.x by a wide margin. Some compatibility issues could pose a problem, but most developers have nothing to worry about.
In this post, Toptal Freelance Software Engineer Vilson Duka explains what makes PHP 7 different, and why it's time to make the switch.