What is PHP 7 and what major features did it introduce?

PHP 7 (released December 2015) was a landmark release that doubled performance over PHP 5 through a new Zend Engine 3 with the PHPNG (PHP Next Generation) optimizations. Key new features: scalar type declarations (int, float, string, bool for parameters and returns), return type declarations, null coalescing operator (??), spaceship operator (<=>), anonymous classes, group use declarations, integer division function (intdiv()), uniform variable syntax, and throwable interface (allowing both Errors and Exceptions to be caught with a single catch). It also removed deprecated features like the mysql_* extension. PHP 7 made PHP a genuinely competitive language for high-performance applications.