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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 326298 $ -->
<refentry xml:id="splobjectstorage.gethash" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<refnamediv>
<refname>SplObjectStorage::getHash</refname>
<refpurpose>
Calculate a unique identifier for the contained objects
</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<modifier>public</modifier> <type>string</type><methodname>SplObjectStorage::getHash</methodname>
<methodparam><type>object</type><parameter>object</parameter></methodparam>
</methodsynopsis>
<para>
This method calculates an identifier for the objects added to an
<classname>SplObjectStorage</classname> object.
</para>
<para>
The implementation in <classname>SplObjectStorage</classname> returns
the same value as <function>spl_object_hash</function>.
</para>
<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.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<variablelist>
<varlistentry>
<term><parameter>object</parameter></term>
<listitem>
<para>
The object whose identifier is to be calculated.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
A <type>string</type> with the calculated identifier.
</para>
</refsect1>
<refsect1 role="errors">
&reftitle.errors;
<para>
A <classname>RuntimeException</classname> is thrown when the returned
value is not a <type>string</type>.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>SplObjectStorage::getHash</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
class OneSpecimenPerClassStorage extends SplObjectStorage {
public function getHash($o) {
return get_class($o);
}
}
class A {}
$s = new OneSpecimenPerClassStorage;
$o1 = new stdClass;
$o2 = new stdClass;
$o3 = new A;
$s[$o1] = 1;
//$o2 is considered equal to $o1 so the value is replaced
$s[$o2] = 2;
$s[$o3] = 3;
//these are considered equal to the objects before
//so they can be used to access the values stored under them
$p1 = new stdClass;
$p2 = new A;
echo $s[$p1], "\n";
echo $s[$p2], "\n";
?>
]]>
</programlisting>
&example.outputs.similar;
<screen>
<![CDATA[
2
3
]]>
</screen>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>spl_object_hash</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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