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<h1>Event callbacks</h1>
<p class="para">
If a callback is registered for an event, it will be called when the event
becomes active. To associate a callback with event one can pass a
<span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span>
to either
<span class="methodname"><a href="event.construct.html" class="methodname">Event::__construct()</a></span>
, or
<span class="methodname"><a href="event.set.html" class="methodname">Event::set()</a></span>
, or one of the factory methods like
<span class="methodname"><a href="event.timer.html" class="methodname">Event::timer()</a></span>
.
</p>
<p class="para">
An event callback should match the following prototype:
</p>
<div class="methodsynopsis dc-description">
<span class="type"><span class="type void">void</span></span>
<span class="methodname"><strong>callback</strong></span>
([ <span class="methodparam">
<span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span>
<code class="parameter">$fd</code>
<span class="initializer"> = <strong><code>NULL</code></strong></span>
</span>
[, <span class="methodparam">
<span class="type">int</span>
<code class="parameter">$what</code>
</span>
[, <span class="methodparam">
<span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span>
<code class="parameter">$arg</code>
<span class="initializer"> = <strong><code>NULL</code></strong></span>
</span>
]]] )</div>
<p class="para">
<dl>
<dt>
<code class="parameter">fd</code>
</dt>
<dd>
<p class="para">
The file descriptor, stream resource or socket associated with the
event. For signal event
<code class="parameter">fd</code>
is equal to the signal number.
</p>
</dd>
<dt>
<code class="parameter">what</code>
</dt>
<dd>
<p class="para">
Bit mask of
<em class="emphasis">all</em>
events triggered.
</p>
</dd>
<dt>
<code class="parameter">arg</code>
</dt>
<dd>
<p class="para">
User custom data.
</p>
</dd>
</dl>
</p>
<p class="para">
<span class="methodname"><a href="event.timer.html" class="methodname">Event::timer()</a></span>
expects the callback to match the following prototype:
</p>
<div class="methodsynopsis dc-description">
<span class="type"><span class="type void">void</span></span>
<span class="methodname"><strong>callback</strong></span>
([ <span class="methodparam">
<span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span>
<code class="parameter">$arg</code>
<span class="initializer"> = <strong><code>NULL</code></strong></span>
</span>
] )</div>
<p class="para">
<dl>
<dt>
<code class="parameter">arg</code>
</dt>
<dd>
<p class="para">
User custom data.
</p>
</dd>
</dl>
</p>
<p class="para">
<span class="methodname"><a href="event.signal.html" class="methodname">Event::signal()</a></span>
expects the callback to match the following prototype:
</p>
<div class="methodsynopsis dc-description">
<span class="type"><span class="type void">void</span></span>
<span class="methodname"><strong>callback</strong></span>
([ <span class="methodparam">
<span class="type">int</span>
<code class="parameter">$signum</code>
</span>
[, <span class="methodparam">
<span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span>
<code class="parameter">$arg</code>
<span class="initializer"> = <strong><code>NULL</code></strong></span>
</span>
]] )</div>
<p class="para">
<dl>
<dt>
<code class="parameter">signum</code>
</dt>
<dd>
<p class="para">
The number of the triggered signal(e.g.
<strong><code>SIGTERM</code></strong>
).
</p>
</dd>
<dt>
<code class="parameter">arg</code>
</dt>
<dd>
<p class="para">
User custom data.
</p>
</dd>
</dl>
</p>
</div>
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