PHP 7.X provides major performance improvements over PHP 5.6. Benchmark tests showed WordPress running 2.7x faster on PHP 7 than PHP 5.6. New features in PHP 7 include scalar type declarations, return type declarations, the null coalescing operator, and anonymous classes. PHP 7.1 introduced nullable types, void functions, and catch exception handling. PHP 7.2 includes support for Argon2 password hashing and deprecates create_function().