The Birth of PHP 6;
After Version 5: PHP received mixed reviews due to lacking native Unicode support at the core language level. In 2005, a project headed by Andrei Zmievski was initiated to bring native Unicode support throughout PHP, by embedding the International Components for Unicode (ICU) library, and representing text strings as UTF-16 internally. Since this would cause major changes both to the internals of the language and to user code, it was planned to release this as version 6.0 of the language, along with other major features then in development.
The Birth of PHP 7;
During 2014 and 2015, a new major PHP version was developed, PHP 7. The numbering of this version involved some debate among internal developers.While the PHP 6 Unicode experiment had never been released, several articles and book titles referenced the PHP 6 name, which might have caused confusion if a new release were to reuse the name. After a vote, the name PHP 7 was chosen.
The foundation of PHP 7 is a PHP branch that was originally dubbed PHP next generation (phpng). It was authored by Dmitry Stogov, Xinchen Hui and Nikita Popov, and aimed to optimize PHP performance by refactoring the Zend Engine while retaining near-complete language compatibility. By 14 July 2014, WordPress-based benchmarks, which served as the main benchmark suite for the phpng project, showed an almost 100% increase in performance. Changes from phpng make it easier to improve performance in future versions, as more compact data structures and other changes are seen as better suited for a successful migration to a just-in-time (JIT) compiler. Because of the significant changes, the reworked Zend Engine was called Zend Engine 3, succeeding Zend Engine 2 used in PHP 5.
Because of the major internal changes in phpng, it must receive a new major version number of PHP, rather than a minor PHP 5 release, according to PHP's release process. Major versions of PHP are allowed to break backward-compatibility of code and therefore PHP 7 presented an opportunity for other improvements beyond phpng that require backward-compatibility breaks.
The Birth of PHP 8;
PHP 8 was released on November 26, 2020. PHP 8 is a major version and has breaking changes from previous versions.New features and notable changes include:
Just-in-time compilation
Just-in-time compilation is supported in PHP 8.
PHP 8's JIT compiler can provide substantial performance improvements for some use cases.PHP developer Nikita Popov has stated that the performance improvements for most websites will be less substantial than the upgrade from PHP 5 to PHP 7.Performance improvements due to the addition of the JIT compiler are expected to be more substantial for mathematical-type operations than for common web-development use cases.Additionally, the JIT compiler provides future potential to move some code from C to PHP, due to the performance improvements for some use cases.
Addition of the match expression
Main article: PHP syntax and semantics § Match
PHP 8 introduced the match expression.The match expression is conceptually similar to a switch statement and is more compact for some use cases.Because match is an expression, its result can be caught into a variable or returned from a function.
Type changes and additions
PHP 8 introduced union types, a new static return type, and a new mixed type.
"Attributes", often referred to as "annotations" in other programming languages, were added in PHP 8, which allow metadata to be added to classes.
throw was changed from being a statement to being an expression. This allows exceptions to be thrown in places that were not previously possible. Sorce: wikipedia
