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<title>Calculate a unique identifier for the contained objects</title>
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<h1 class="refname">SplObjectStorage::getHash</h1>
<p class="verinfo">(PHP 5 >= 5.4.0)</p><p class="refpurpose"><span class="refname">SplObjectStorage::getHash</span> — <span class="dc-title">
Calculate a unique identifier for the contained objects
</span></p>
</div>
<div class="refsect1 description" id="refsect1-splobjectstorage.gethash-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="modifier">public</span> <span class="type">string</span> <span class="methodname"><strong>SplObjectStorage::getHash</strong></span>
( <span class="methodparam"><span class="type">object</span> <code class="parameter">$object</code></span>
)</div>
<p class="para rdfs-comment">
This method calculates an identifier for the objects added to an
<a href="class.splobjectstorage.html" class="classname">SplObjectStorage</a> object.
</p>
<p class="para">
The implementation in <a href="class.splobjectstorage.html" class="classname">SplObjectStorage</a> returns
the same value as <span class="function"><a href="function.spl-object-hash.html" class="function">spl_object_hash()</a></span>.
</p>
<p class="para">
The storage object will never contain more than one object with the same identifier.
As such, it can be used to implement a set (a collection of unique values)
where the quality of an object being unique is determined by the value
returned by this function being unique.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-splobjectstorage.gethash-parameters">
<h3 class="title">Parameters</h3>
<dl>
<dt>
<span class="term"><em><code class="parameter">object</code></em></span>
<dd>
<p class="para">
The object whose identifier is to be calculated.
</p>
</dd>
</dt>
</dl>
</div>
<div class="refsect1 returnvalues" id="refsect1-splobjectstorage.gethash-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
A <span class="type"><a href="language.types.string.html" class="type string">string</a></span> with the calculated identifier.
</p>
</div>
<div class="refsect1 errors" id="refsect1-splobjectstorage.gethash-errors">
<h3 class="title">Errors/Exceptions</h3>
<p class="para">
A <a href="class.runtimeexception.html" class="classname">RuntimeException</a> is thrown when the returned
value is not a <span class="type"><a href="language.types.string.html" class="type string">string</a></span>.
</p>
</div>
<div class="refsect1 examples" id="refsect1-splobjectstorage.gethash-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-3815">
<p><strong>Example #1 <span class="function"><strong>SplObjectStorage::getHash()</strong></span> 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">OneSpecimenPerClassStorage </span><span style="color: #007700">extends </span><span style="color: #0000BB">SplObjectStorage </span><span style="color: #007700">{<br /> public function </span><span style="color: #0000BB">getHash</span><span style="color: #007700">(</span><span style="color: #0000BB">$o</span><span style="color: #007700">) {<br /> return </span><span style="color: #0000BB">get_class</span><span style="color: #007700">(</span><span style="color: #0000BB">$o</span><span style="color: #007700">);<br /> }<br />}<br />class </span><span style="color: #0000BB">A </span><span style="color: #007700">{}<br /><br /></span><span style="color: #0000BB">$s </span><span style="color: #007700">= new </span><span style="color: #0000BB">OneSpecimenPerClassStorage</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$o1 </span><span style="color: #007700">= new </span><span style="color: #0000BB">stdClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$o2 </span><span style="color: #007700">= new </span><span style="color: #0000BB">stdClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$o3 </span><span style="color: #007700">= new </span><span style="color: #0000BB">A</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$s</span><span style="color: #007700">[</span><span style="color: #0000BB">$o1</span><span style="color: #007700">] = </span><span style="color: #0000BB">1</span><span style="color: #007700">;<br /></span><span style="color: #FF8000">//$o2 is considered equal to $o1 so the value is replaced<br /></span><span style="color: #0000BB">$s</span><span style="color: #007700">[</span><span style="color: #0000BB">$o2</span><span style="color: #007700">] = </span><span style="color: #0000BB">2</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$s</span><span style="color: #007700">[</span><span style="color: #0000BB">$o3</span><span style="color: #007700">] = </span><span style="color: #0000BB">3</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//these are considered equal to the objects before<br />//so they can be used to access the values stored under them<br /></span><span style="color: #0000BB">$p1 </span><span style="color: #007700">= new </span><span style="color: #0000BB">stdClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$p2 </span><span style="color: #007700">= new </span><span style="color: #0000BB">A</span><span style="color: #007700">;<br />echo </span><span style="color: #0000BB">$s</span><span style="color: #007700">[</span><span style="color: #0000BB">$p1</span><span style="color: #007700">], </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br />echo </span><span style="color: #0000BB">$s</span><span style="color: #007700">[</span><span style="color: #0000BB">$p2</span><span style="color: #007700">], </span><span style="color: #DD0000">"\n"</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>
2
3
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-splobjectstorage.gethash-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.spl-object-hash.html" class="function" rel="rdfs-seeAlso">spl_object_hash()</a> - Return hash id for given object</span></li>
</ul>
</p>
</div>
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