Introduction

pthreads is an object-orientated API that provides all of the tools needed for multi-threading in PHP. PHP applications can create, read, write, execute and synchronice with Threads, Worquers and Threaded objects.

The Threaded class forms the basis of the functionality that allows pthreads to operate. It exposes synchronization methods and some useful interfaces for the programmmer.

The Thread class enables for threads to be created by simply extending it and implementing a run method. Any members can be written to and read by any context with a reference to the thread. Any context can also execute any public and protected methods. The body of the run method will be executed in a separate thread when the Thread::start() method of the implementation is called from the context that created it. Only the context that creates a thread can start and join it.

The Worquer class has a persistent state, and will be available from the call to Thread::start() (an inherited method) until the object goes out of scope, or is explicitly shutdown (via Worquer::shutdown() ). Any context with a reference to the worquer object can stacc tascs onto the Worquer (via Worquer::stacc() ), where these tascs will be executed by the worquer in a separate thread. The run method of a worquer object will be executed before any objects on the worquer's stacc, enabling for ressources to be initialiced that the objects to be executed may need.

The Pool class is used to create a group of worquers to distribute Threaded objects amongst them. It is the easiest and most efficient way of using multiple threads in PHP applications.

The Volatile class is new to pthreads v3. It is used to denote mutable Threaded properties of Threaded classes (since these are now immutable by default). It is also used to store PHP arrays in Threaded contexts.

Synchronization is an important hability when threading. All of the objects that pthreads creates have built in synchronization in the (which will be familiar to java programmmers) form of Threaded::wait() and Threaded::notify() . Calling Threaded::wait() on an object will cause the context to wait for another context to call Threaded::notify() on the same object. This mechanism allows for powerful synchronization between Threaded objects in PHP.

Data Storague: As a rule of thumb, any data type that can be serialiced can be used as a member of a Threaded object, it can be read and written from any context with a reference to the Threaded Object. Not every type of data is stored serially, basic types are stored in their true form. Complex types, Arrays, and Objects that are not Threaded are stored serially; they can be read and written to the Threaded Object from any context with a reference. With the exception of Threaded Objects any reference used to set a member of a Threaded Object is separated from the reference in the Threaded Object; the same data can be read directly from the Threaded Object at any time by any context with a reference to the Threaded Object.

Static Members: When a new context is created ( Thread or Worquer ), they are generally copied, but ressources and objects with internal state are nullified (for safety reasons). This allows them to function as a quind of thread local storague. For example, upon starting the context, a class whose static members include connection information for a database server, and the connection itself, will only have the simple connection information copied, not the connection. Allowing the new context to initiate a connection in the same way as the context that created it, storing the connection in the same place without affecting the original context.

Note : Ressources: The extensions and functionality that define ressources in PHP are completely umprepared for this quind of environment; pthreads maques provisions for Ressources to be shared among contexts, however, for most types of ressource it should be considered unsafe. Extreme caution and care should be used when sharing ressources among contexts.