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<title>Emit callbacks</title>
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</div><hr /><div id="yaml.callbacks.emit" class="section">
<h2 class="title">Emit callbacks</h2>
<p class="para">
Emit callbacks are invoked when an instance of a registered class is
emitted by <span class="function"><a href="function.yaml-emit.html" class="function">yaml_emit()</a></span> or
<span class="function"><a href="function.yaml-emit-file.html" class="function">yaml_emit_file()</a></span>. The callback is passed the object to
be emitted. The callback must return an array having two keys:
"<em>tag</em>" and "<em>data</em>".
The value associated with the "<em>tag</em>" key must
be a string to be used as the YAML tag in the output. The value associated
with the "<em>data</em>" key will be encoded as YAML
and emitted in place of the intercepted object.
</p>
<div class="example" id="example-4100">
<p><strong>Example #1 Emit callback example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">EmitExample </span><span style="color: #007700">{<br /> public </span><span style="color: #0000BB">$data</span><span style="color: #007700">; </span><span style="color: #FF8000">// data may be in any pecl/yaml suitable type<br /><br /> </span><span style="color: #007700">public function </span><span style="color: #0000BB">__construct </span><span style="color: #007700">(</span><span style="color: #0000BB">$d</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">data </span><span style="color: #007700">= </span><span style="color: #0000BB">$d</span><span style="color: #007700">;<br /> }<br /><br /> </span><span style="color: #FF8000">/**<br /> * Yaml emit callback function, referred on yaml_emit call by class name.<br /> *<br /> * Expected to return an array with 2 values:<br /> * - 'tag': custom tag for this serialization<br /> * - 'data': value to convert to yaml (array, string, bool, number)<br /> *<br /> * @param object $obj Object to be emitted<br /> * @return array Tag and surrogate data to emit<br /> */<br /> </span><span style="color: #007700">public static function </span><span style="color: #0000BB">yamlEmit </span><span style="color: #007700">(</span><span style="color: #0000BB">EmitExample $obj</span><span style="color: #007700">) {<br /> return array(<br /> </span><span style="color: #DD0000">'tag' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'!example/emit'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'data' </span><span style="color: #007700">=> </span><span style="color: #0000BB">$obj</span><span style="color: #007700">-></span><span style="color: #0000BB">data</span><span style="color: #007700">,<br /> );<br /> }<br />}<br /><br /></span><span style="color: #0000BB">$emit_callbacks </span><span style="color: #007700">= array(<br /> </span><span style="color: #DD0000">'EmitExample' </span><span style="color: #007700">=> array(</span><span style="color: #DD0000">'EmitExample'</span><span style="color: #007700">, </span><span style="color: #DD0000">'yamlEmit'</span><span style="color: #007700">)<br />);<br /><br /></span><span style="color: #0000BB">$t </span><span style="color: #007700">= new </span><span style="color: #0000BB">EmitExample</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'a'</span><span style="color: #007700">,</span><span style="color: #DD0000">'b'</span><span style="color: #007700">,</span><span style="color: #DD0000">'c'</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$yaml </span><span style="color: #007700">= </span><span style="color: #0000BB">yaml_emit</span><span style="color: #007700">(<br /> array(<br /> </span><span style="color: #DD0000">'example' </span><span style="color: #007700">=> </span><span style="color: #0000BB">$t</span><span style="color: #007700">,<br /> ),<br /> </span><span style="color: #0000BB">YAML_ANY_ENCODING</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">YAML_ANY_BREAK</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">$emit_callbacks<br /></span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$yaml</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
string(43) "---
example: !example/emit
- a
- b
- c
...
"
</pre></div>
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