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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.serialize" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>serialize</refname>
<refpurpose>Generates a storable representation of a value</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>string</type><methodname>serialize</methodname>
<methodparam><type>mixed</type><parameter>value</parameter></methodparam>
</methodsynopsis>
<para>
Generates a storable representation of a value.
</para>
<para>
This is useful for storing or passing PHP values around without
losing their type and structure.
</para>
<para>
To make the serialized string into a PHP value again, use
<function>unserialize</function>.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>value</parameter></term>
<listitem>
<para>
The value to be serialized. <function>serialize</function>
handles all types, except the <type>resource</type>-type and some <type>object</type>s (see note below).
You can even <function>serialize</function> arrays that contain
references to itself. Circular references inside the array/object you
are serializing will also be stored. Any other
reference will be lost.
</para>
<para>
When serializing objects, PHP will attempt to call the member functions
<link linkend="object.serialize">__serialize()</link> or
<link linkend="object.sleep">__sleep()</link> prior to serialization.
This is to allow the object to do any last minute clean-up, etc. prior
to being serialized. Likewise, when the object is restored using
<function>unserialize</function> the <link linkend="object.unserialize">__unserialize()</link> or
<link linkend="object.wakeup">__wakeup()</link> member function is called.
</para>
<note>
<para>
Object's private members have the class name prepended to the member
name; protected members have a '*' prepended to the member name.
These prepended values have null bytes on either side.
</para>
</note>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns a string containing a byte-stream representation of
<parameter>value</parameter> that can be stored anywhere.
</para>
<para>
Note that this is a binary string which may include null bytes, and needs
to be stored and handled as such. For example,
<function>serialize</function> output should generally be stored in a BLOB
field in a database, rather than a CHAR or TEXT field.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>serialize</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
// $session_data contains a multi-dimensional array with session
// information for the current user. We use serialize() to store
// it in a database at the end of the request.
$conn = odbc_connect("webdb", "php", "chicken");
$stmt = odbc_prepare($conn,
"UPDATE sessions SET data = ? WHERE id = ?");
$sqldata = array (serialize($session_data), $_SERVER['PHP_AUTH_USER']);
if (!odbc_execute($stmt, $sqldata)) {
$stmt = odbc_prepare($conn,
"INSERT INTO sessions (id, data) VALUES(?, ?)");
if (!odbc_execute($stmt, array_reverse($sqldata))) {
/* Something went wrong.. */
}
}
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
<note>
<para>
Note that many built-in PHP objects cannot be serialized. However, those with
this ability either implement the <interfacename>Serializable</interfacename> interface or the
magic <link linkend="object.serialize">__serialize()</link>/<link linkend="object.unserialize">__unserialize()</link>
or <link linkend="object.sleep">__sleep()</link>/<link linkend="object.wakeup">__wakeup()</link> methods. If an
internal class does not fulfill any of those requirements, it cannot reliably be
serialized.
</para>
<para>
There are some historical exceptions to the above rule, where some internal objects
could be serialized without implementing the interface or exposing the methods.
</para>
</note>
<warning>
<para>
When <function>serialize</function> serializes objects, the leading backslash is not included in the class name of namespaced classes for maximum compatibility.
</para>
</warning>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>unserialize</function></member>
<member><function>var_export</function></member>
<member><function>json_encode</function></member>
<member><link linkend="language.oop5.serialization">Serializing Objects</link></member>
<member><link linkend="object.sleep">__sleep()</link></member>
<member><link linkend="object.wakeup">__wakeup()</link></member>
<member><link linkend="object.serialize">__serialize()</link></member>
<member><link linkend="object.unserialize">__unserialize()</link></member>
</simplelist>
</para>
</refsect1>
</refentry>
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