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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.5 $ -->
<!-- splitted from ./en/functions/session.xml, last change in rev 1.2 -->
<refentry id="function.session-start">
<refnamediv>
<refname>session_start</refname>
<refpurpose>Initialize session data</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<methodsynopsis>
<type>bool</type><methodname>session_start</methodname>
<void/>
</methodsynopsis>
<simpara>
<function>session_start</function> creates a session or resumes
the current one based on the current session id that's being
passed via a request, such as GET, POST, or a cookie.
</simpara>
<simpara>
This function always returns &true;.
</simpara>
<note>
<para>
If you are using cookie-based sessions, you must call
<function>session_start</function> before anything is outputted to the
browser.
</para>
</note>
<para>
<example>
<title>A session example: <filename>page1.php</filename></title>
<programlisting role="php">
<![CDATA[
<?php
// page1.php
session_start();
echo 'Welcome to page #1';
$_SESSION['favcolor'] = 'green';
$_SESSION['animal'] = 'cat';
$_SESSION['time'] = time();
// Works if session cookie was accepted
echo '<br /><a href="page2.php">page 2</a>';
// Or maybe pass along the session id, if needed
echo '<br /><a href="page2.php?' . SID . '">page 2</a>';
?>
]]>
</programlisting>
</example>
</para>
<para>
After viewing <filename>page1.php</filename>, the second page
<filename>page2.php</filename> will magically contain the session
data. Read the <link linkend="ref.session">session reference</link>
for information on <link linkend="session.idpassing">propagating
session ids</link> as it, for example, explains what the constant
<constant>SID</constant> is all about.
</para>
<para>
<example>
<title>A session example: <filename>page2.php</filename></title>
<programlisting role="php">
<![CDATA[
<?php
// page2.php
session_start();
echo 'Welcome to page #2<br />';
echo $_SESSION['favcolor']; // green
echo $_SESSION['animal']; // cat
echo date('Y m d H:i:s', $_SESSION['time']);
// You may want to use SID here, like we did in page1.php
echo '<br /><a href="page1.php">page 1</a>';
?>
]]>
</programlisting>
</example>
</para>
<simpara>
If you want to use a named session, you must call
<function>session_name</function> before calling
<function>session_start</function>.
</simpara>
<simpara>
<function>session_start</function> will register internal output
handler for URL rewriting when <literal>trans-sid</literal> is
enabled. If a user uses <literal>ob_gzhandler</literal> or like
with <function>ob_start</function>, the order of output handler
is important for proper output. For example, user must register
<literal>ob_gzhandler</literal> before session start.
</simpara>
<note>
<simpara>
Use of <link linkend="ini.zlib.output-compression">zlib.output_compression</link>
is recommended rather than <function>ob_gzhandler</function>
</simpara>
</note>
<note>
<para>
As of PHP 4.3.3, calling <function>session_start</function> while the
session has already been started will result in an error of level
<constant>E_NOTICE</constant>. Also, the second session start will
simply be ignored.
</para>
</note>
<para>
See also
<link linkend="reserved.variables.session">$_SESSION</link>,
<link linkend="ini.session.auto-start">session.auto_start</link>, and
<function>session_id</function>.
</para>
</refsect1>
</refentry>
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