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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><title>SetCallback</title><link rel="stylesheet" type="text/css" href="phplotdoc.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /><link rel="home" href="index.html" title="PHPlot Reference Manual" /><link rel="up" href="reference.html" title="PHPlot Function Reference" /><link rel="prev" href="SetBrowserCache.html" title="SetBrowserCache" /><link rel="next" href="SetDataBorderColors.html" title="SetDataBorderColors" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">SetCallback</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="SetBrowserCache.html">Prev</a> </td><th width="60%" align="center">PHPlot Function Reference</th><td width="20%" align="right"> <a accesskey="n" href="SetDataBorderColors.html">Next</a></td></tr></table><hr /></div><div class="refentry"><a id="SetCallback"></a><div class="titlepage"></div><div class="refnamediv"><h2><span class="refentrytitle">SetCallback</span></h2><p>SetCallback &#8212; Registers a callback function</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">$plot-&gt;SetCallback(<em class="parameter"><code>$reason</code></em>, <em class="parameter"><code>$function</code></em>, [<span class="optional"><em class="parameter"><code>$arg</code></em></span>])</pre></div><div class="refsect1"><a id="idp1377821860"></a><h2>Description</h2><p>
<code class="function">SetCallback</code> registers a callback function. That is, it
arranges for the caller-provided function to be called at a specific point
or points inside PHPlot's internal processing.
    </p></div><div class="refsect1"><a id="idp1377822972"></a><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="replaceable"><code>$reason</code></em></span></dt><dd><p>
A PHPlot-defined name for the callback.
See <a class="xref" href="callbacks.html#callbacks-names" title="4.4.3. Available Callbacks">Section 4.4.3, &#8220;Available Callbacks&#8221;</a>.
          </p></dd><dt><span class="term"><em class="replaceable"><code>$function</code></em></span></dt><dd><p>
The function to be called. This can be either the name of a function as a
string, or a two-element array with an object class instance and method name.
See <a class="xref" href="callbacks.html#callbacks-api" title="4.4.1. Callbacks Application Interface">Section 4.4.1, &#8220;Callbacks Application Interface&#8221;</a> for more information.
          </p></dd><dt><span class="term"><em class="replaceable"><code>$arg</code></em></span></dt><dd><p>
An optional opaque argument passed-through to the callback function when
PHPlot triggers the callback. If not supplied, the callback function will
get a NULL argument.
          </p></dd></dl></div></div><div class="refsect1"><a id="idp1377827276"></a><h2>Return Value</h2><p>
Returns True if the callback has been registered.
Returns False on error. The only error condition is if the given callback
reason is not valid. Note that the function name is not validated until
the callback is triggered.
    </p></div><div class="refsect1"><a id="idp1377828092"></a><h2>Notes</h2><p>
If a callback is already registered for the given reason, the new callback
replaces the old one.
    </p><p>
Refer to <a class="xref" href="callbacks.html" title="4.4. Callbacks">Section 4.4, &#8220;Callbacks&#8221;</a> for more information on callbacks.
    </p></div><div class="refsect1"><a id="idp1377829388"></a><h2>History</h2><p>
This function and the callbacks implementation were added in PHPlot-5.0.4
as an experimental feature. Callbacks were first documented in this manual
as of PHPlot-5.0.5 and are no longer considered experimental.
    </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="SetBrowserCache.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="reference.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="SetDataBorderColors.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">SetBrowserCache </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> SetDataBorderColors</td></tr></table></div></body></html>