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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 311151 $ -->
<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.shm-attach">
<refnamediv>
<refname>shm_attach</refname>
<refpurpose>Creates or open a shared memory segment</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>resource</type><methodname>shm_attach</methodname>
<methodparam><type>int</type><parameter>key</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>memsize</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>perm</parameter><initializer>0666</initializer></methodparam>
</methodsynopsis>
<para>
<function>shm_attach</function> returns an id that can be used to access
the System V shared memory with the given <parameter>key</parameter>, the
first call creates the shared memory segment with
<parameter>memsize</parameter> and the optional perm-bits
<parameter>perm</parameter>.
</para>
<para>
A second call to <function>shm_attach</function> for the same
<parameter>key</parameter> will return a different shared memory
identifier, but both identifiers access the same underlying
shared memory. <parameter>memsize</parameter> and
<parameter>perm</parameter> will be ignored.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>key</parameter></term>
<listitem>
<para>
A numeric shared memory segment ID
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>memsize</parameter></term>
<listitem>
<para>
The memory size. If not provided, default to the
<literal>sysvshm.init_mem</literal> in the &php.ini;, otherwise 10000
bytes.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>perm</parameter></term>
<listitem>
<para>
The optional permission bits. Default to 0666.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns a shared memory segment identifier.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>5.3.0</entry>
<entry>
This function now returns a &resource; instead of an
<link linkend="language.types.integer">integer</link>.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
<note>
<para>
This function used to return an integer value prior to
PHP 5.3.0. To achieve the same value in a portable manner, the
return value can be cast to an integer like:
</para>
<para>
<example>
<programlisting role="php">
<![CDATA[
<?php
// Create a temporary file and return its path
$tmp = tempnam('/tmp', 'PHP');
// Get the file token key
$key = ftok($tmp, 'a');
// Attach the SHM resource, notice the cast afterwards
$id = shm_attach($key);
if ($id === false) {
die('Unable to create the shared memory segment');
}
// Cast to integer, since prior to PHP 5.3.0 the resource id
// is returned which can be exposed when casting a resource
// to an integer
$id = (integer) $id;
?>
]]>
</programlisting>
</example>
</para>
</note>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>shm_detach</function></member>
<member><function>ftok</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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