shm-attach.xml

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<refentry xml:id="function.shm-attach" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>shm_attach</refname>
  <refpurpose>Creates or open a shared memory segment</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>SysvSharedMemory</type><type>false</type></type><methodname>shm_attach</methodname>
   <methodparam><type>int</type><parameter>key</parameter></methodparam>
   <methodparam choice="opt"><type class="union"><type>int</type><type>null</type></type><parameter>size</parameter><initializer>&null;</initializer></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>permissions</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>size</parameter> and the optional perm-bits 
   <parameter>permissions</parameter>.
  </para>
  <para>
   A second call to <function>shm_attach</function> for the same
   <parameter>key</parameter> will return a different <classname>SysvSharedMemory</classname>
   instance, but both instances access the same underlying
   shared memory. <parameter>size</parameter> and
   <parameter>permissions</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>size</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>permissions</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 <classname>SysvSharedMemory</classname> instance on success, &return.falseforfailure;.
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>8.0.0</entry>
      <entry>
       On success, this function returns an <classname>SysvSharedMemory</classname> instance now;
       previously, a <type>resource</type> was returned.
      </entry>
     </row>
     <row>
      <entry>8.0.0</entry>
      <entry>
       <parameter>size</parameter> is nullable now.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </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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