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<refentry xml:id="function.apc-define-constants" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>apc_define_constants</refname>
  <refpurpose>
   Defines a set of constants for retrieval and mass-definition 
  </refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>apc_define_constants</methodname>
   <methodparam><type>string</type><parameter>key</parameter></methodparam>
   <methodparam><type>array</type><parameter>constants</parameter></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter>case_sensitive</parameter></methodparam>
  </methodsynopsis>

  <para>
   <function>define</function> is notoriously slow. Since the main benefit of
   APC is to increase the performance of scripts/applications, this mechanism
   is provided to streamline the process of mass constant definition. However,
   this function does not perform as well as anticipated.
  </para>

  <para>
   For a better-performing solution, try the
   <link xlink:href="&url.pecl.package;hidef">hidef</link> extension from PECL.
  </para>

  <note>
   <simpara>
    To remove a set of stored constants (without clearing the entire cache), an
    empty array may be passed as the <parameter>constants</parameter>
    parameter, effectively clearing the stored value(s).
   </simpara>
  </note>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>key</parameter></term>
     <listitem>
      <para>
       The <parameter>key</parameter> serves as the name of the constant set
       being stored. This <parameter>key</parameter> is used to retrieve the
       stored constants in <function>apc_load_constants</function>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>constants</parameter></term>
     <listitem>
      <para>
       An associative array of <literal>constant_name => value</literal>
       pairs. The <literal>constant_name</literal> must follow the normal
       <link linkend="language.constants">constant</link> naming rules.
       <literal>value</literal> must evaluate to a scalar value.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>case_sensitive</parameter></term>
     <listitem>
      <para>
       The default behaviour for constants is to be declared case-sensitive;
       i.e. <literal>CONSTANT</literal> and <literal>Constant</literal>
       represent different values. If this parameter evaluates to &false; the
       constants will be declared as case-insensitive symbols.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
 </refsect1>


 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>apc_define_constants</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$constants = array(
    'ONE'   => 1,
    'TWO'   => 2,
    'THREE' => 3,
);
apc_define_constants('numbers', $constants);
echo ONE, TWO, THREE;
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
123
]]>
    </screen>
   </example>
  </para>
 </refsect1>


 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>apc_load_constants</function></member>
    <member><function>define</function></member>
    <member><function>constant</function></member>
    <member>
     Or <link linkend="language.constants">the PHP constants reference</link>
    </member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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