2002-04-15 00:12:54 +00:00
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<?xml version="1.0" encoding="iso-8859-1"?>
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2002-04-17 06:45:35 +00:00
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<!-- $Revision: 1.2 $ -->
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2002-04-15 00:12:54 +00:00
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<!-- splitted from ./en/functions/funchand.xml, last change in rev 1.1 -->
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<refentry id="function.function-exists">
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<refnamediv>
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<refname>function_exists</refname>
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<refpurpose>
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Return &true; if the given function has been defined
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</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<methodsynopsis>
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<type>bool</type><methodname>function_exists</methodname>
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<methodparam><type>string</type><parameter>function_name</parameter></methodparam>
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</methodsynopsis>
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<para>
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Checks the list of defined functions, both built-in (internal) and
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user-defined, for <parameter>function_name</parameter>. &return.success;
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<informalexample>
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<programlisting role="php">
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<![CDATA[
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if (function_exists('imap_open')) {
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echo "IMAP functions are available.<br>\n";
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} else {
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echo "IMAP functions are not available.<br>\n";
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}
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]]>
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</programlisting>
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</informalexample>
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Note that a function name may exist even if the function itself
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is unusable due to configuration or compiling options (with the
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<link linkend="ref.image">image</link> functions being an example).
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Also note that <function>function_exists</function> will return
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&false; for constructs, such as <function>include_once</function>
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and <function>echo</function>.
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</para>
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<para>
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See also <function>method_exists</function> and
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<function>get_defined_functions</function>.
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"../../../../manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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