mirror of
https://github.com/sigmasternchen/php-doc-en
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a9b26c34e4
Side effect of this change is that include, require and return are now properly linked. They weren't because they don't live inside <refentry> so PhD doesn't know about them. git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@324522 c90b9560-bf6c-de11-be94-00142212c4b1
116 lines
3 KiB
XML
116 lines
3 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<refentry xml:id="function.function-exists" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>function_exists</refname>
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<refpurpose>Return &true; if the given function has been defined</refpurpose>
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</refnamediv>
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<refsect1 role="description">
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&reftitle.description;
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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>.
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</para>
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</refsect1>
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<refsect1 role="parameters">
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&reftitle.parameters;
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<para>
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<variablelist>
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<varlistentry>
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<term><parameter>function_name</parameter></term>
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<listitem>
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<para>
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The function name, as a string.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect1>
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<refsect1 role="returnvalues">
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&reftitle.returnvalues;
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<para>
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Returns &true; if <parameter>function_name</parameter> exists and is a
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function, &false; otherwise.
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</para>
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<note>
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<para>
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This function will return &false; for constructs, such as
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<link linkend="function.include-once"><literal>include_once</literal></link> and <link linkend="function.echo"><literal>echo</literal></link>.
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</para>
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</note>
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</refsect1>
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<refsect1 role="examples">
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&reftitle.examples;
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<para>
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<example>
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<title><function>function_exists</function> example</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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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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]]>
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</programlisting>
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</example>
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</para>
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</refsect1>
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<refsect1 role="notes">
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&reftitle.notes;
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<note>
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<para>
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A function name may exist even if the function itself is unusable due to
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configuration or compiling options (with the <link
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linkend="ref.image">image</link> functions being an example).
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</para>
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</note>
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</refsect1>
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<refsect1 role="seealso">
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&reftitle.seealso;
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<para>
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<simplelist>
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<member><function>method_exists</function></member>
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<member><function>is_callable</function></member>
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<member><function>get_defined_functions</function></member>
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<member><function>class_exists</function></member>
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<member><function>extension_loaded</function></member>
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</simplelist>
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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:"~/.phpdoc/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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