pht is a new threading extension for PHP. It enables for classes, functions, and even entire files to be threaded. Currently, pht can only be used with PHP 7.2. This is due to ZTS mode being unsafe in PHP 7.0 and 7.1. Support for PHP >7.2 is coming soon.
The pht extension should not be used in a web server environment. Threading should be restricted to CLI-based applications only.
The approach to threading that pht takes is to abstract away the thread itself behind a dedicated object (pht\Thread). Tasks are then added to the thread's internal task queue, where they are processed when the thread is started (via pht\Thread::start).
All thread tasks will execute in isolation inside of the newly spawned thread. For class tasks, this means the spawned objects cannot be passed around between threads. By keeping the threading contexts completely separate from one-another, there becomes no need to serialise the properties of threaded objects (which is a necessary evil if such objects have to operate in multiple threads).
The isolation of threading contexts makes the passing around of data between them somewhat problematic. To solve this problem, threadable data structures (pht\HashTable, pht\Vector, and pht\Queue) have been implemented to allow for a two-way communication style between threads, where they expose mutex locks to control their integrity. These data structures can be safely passed around between threads, and manipulated by multiple threads using the mutex locks that have been packed in with them. They are reference-counted across threads, and so they do not need to be explicitly destroyed. This approach to threading means that only the given built-in data structures need to be safely passed around between threads.
Atomic values are also supported by pht. Currently, only an pht\AtomicInteger class exists. Like the threaded data structures, it too can safely be passed around between threads.