As the last official release of php was PHP 5. The community decided to skip the official release for PHP 6 and after a decade they decided to launch the official version as PHP7.
PHP 7 has been praised to be the best ever versions of PHP till now. PHP 7 came out with some important changes over the previous versions of PHP, PHP7 is has praises for good speed and performance.
PHP 7 also introduced new operator and new scalar type declarations. PHP 7 includes some new methods for error handling a new hierarchy, type error and new types such as int, float, string, and boolean.
Some great resources are available which can be used to start learning PHP 7. There are some resources that are available for free and some of them charge for accessing the tutorials. But before going for php7 I will provide some good free resources that will help learn about the previous versions.
1- PHP Manual
2- Tizag tutorial for PHP
3- The Learn PHP Tutorial providing videos
For more important & helpful PHP 7 learning resources click here Best PHP 7 Tutorials For Complete Beginners

