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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.20 $ -->
<!-- splitted from ./en/functions/info.xml, last change in rev 1.29 -->
<refentry id="function.dl">
<refnamediv>
<refname>dl</refname>
<refpurpose>Loads a PHP extension at runtime</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<methodsynopsis>
<type>int</type><methodname>dl</methodname>
<methodparam><type>string</type><parameter>library</parameter></methodparam>
</methodsynopsis>
<para>
Loads the PHP extension given by the parameter
<parameter>library</parameter>. The <parameter>library</parameter>
parameter is <emphasis>only</emphasis> the filename of the extension to
load which also depends on your platform. For example, the <link
linkend="ref.sockets">sockets</link> extension (if compiled as a shared
module, not the default!) would be called <filename>sockets.so</filename>
on Unix platforms whereas it is called
<filename>php_sockets.dll</filename> on the Windows platform.
</para>
<para>
&return.success; If the functionality of loading modules is not available
(see Note) or has been disabled (either by turning it off
<literal>enable_dl</literal> or by enabling &safemode;
in &php.ini;) an <constant>E_ERROR</constant> is emitted
and execution is stopped. If <function>dl</function> fails because the
specified library couldn't be loaded, in addition to &false; an
<constant>E_WARNING</constant> message is emitted.
</para>
<para>
Use <function>extension_loaded</function> to test whether a given
extension is already available or not. This works on both built-in
extensions and dynamically loaded ones (either through &php.ini;
or <function>dl</function>).
</para>
<para>
The <function>dl</function> function is deprecated as of PHP 5.
Use <link linkend="ini.extension">Extension Loading Directives</link>
method instead.
</para>
<example>
<title><function>dl</function> examples</title>
<programlisting role="php">
<![CDATA[
<?php
// Example loading an extension based on OS
if (!extension_loaded('sqlite')) {
if (strtoupper(substr(PHP_OS, 0, 3) == 'WIN')) {
dl('php_sqlite.dll');
} else {
dl('sqlite.so');
}
}
// Or, the PHP_SHLIB_SUFFIX constant is available as of PHP 4.3.0
if (!extension_loaded('sqlite')) {
$prefix = (PHP_SHLIB_SUFFIX == 'dll') ? 'php_' : '';
dl($prefix . 'sqlite.' . PHP_SHLIB_SUFFIX);
}
?>
]]>
</programlisting>
</example>
<para>
The directory where the extension is loaded from depends on your
platform:
</para>
<para>
Windows - If not explicitly set in the &php.ini;, the extension is
loaded from <filename>c:\php4\extensions\</filename> by default.
</para>
<para>
Unix - If not explicitly set in the &php.ini;, the default extension
directory depends on
<itemizedlist>
<listitem>
<simpara>
whether PHP has been built with <literal>--enable-debug</literal> or
not
</simpara>
</listitem>
<listitem>
<simpara>
whether PHP has been built with (experimental) ZTS (Zend Thread Safety)
support or not
</simpara>
</listitem>
<listitem>
<simpara>
the current internal <literal>ZEND_MODULE_API_NO</literal> (Zend
internal module API number, which is basically the date on which a
major module API change happened, e.g. <literal>20010901</literal>)
</simpara>
</listitem>
</itemizedlist>
Taking into account the above, the directory then defaults to
<literal><install-dir>/lib/php/extensions/ <debug-or-not>-<zts-or-not>-ZEND_MODULE_API_NO</literal>,
e.g.
<filename>/usr/local/php/lib/php/extensions/debug-non-zts-20010901</filename>
or
<filename>/usr/local/php/lib/php/extensions/no-debug-zts-20010901</filename>.
</para>
<note>
<para>
<function>dl</function> is <emphasis>not</emphasis> supported in
multithreaded Web servers. Use the <literal>extensions</literal>
statement in your &php.ini; when operating under such
an environment. However, the <literal>CGI</literal> and
<literal>CLI</literal> build are <emphasis role="strong">not</emphasis>
affected !
</para>
</note>
<note>
<para>
<function>dl</function> is case sensitive on Unix platforms.
</para>
</note>
¬e.sm.disabled;
<para>
See also
<link linkend="ini.extension">Extension Loading Directives</link>
and <function>extension_loaded</function>.
</para>
</refsect1>
</refentry>
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