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<h1 class="title">Introduction</h1>
<p class="para">
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.
</p>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
The pht extension should not be used in a web server environment. Threading
should be restricted to CLI-based applications only.
</p>
</div>
<p class="para">
The approach to threading that pht takes is to abstract away the thread
itself behind a dedicated object (<a href="class.pht-thread.html" class="classname">pht\Thread</a>). Tasks are
then added to the thread's internal task queue, where they are processed
when the thread is started (via <span class="methodname"><a href="pht-thread.start.html" class="methodname">pht\Thread::start()</a></span>).
</p>
<p class="para">
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).
</p>
<p class="para">
The isolation of threading contexts makes the passing around of data
between them somewhat problematic. To solve this problem, threadable data
structures (<a href="class.pht-hashtable.html" class="classname">pht\HashTable</a>, <a href="class.pht-vector.html" class="classname">pht\Vector</a>,
and <a href="class.pht-queue.html" class="classname">pht\Queue</a>) 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.
</p>
<p class="para">
Atomic values are also supported by pht. Currently, only an
<a href="class.pht-atomicinteger.html" class="classname">pht\AtomicInteger</a> class exists. Like the threaded data
structures, it too can safely be passed around between threads.
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