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__wakeup() provide further options in terms of object serialisation. git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@330347 c90b9560-bf6c-de11-be94-00142212c4b1
123 lines
4 KiB
XML
123 lines
4 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<sect1 xml:id="language.oop5.serialization" xmlns="http://docbook.org/ns/docbook">
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<title>Object Serialization</title>
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<title>Serializing objects - objects in sessions</title>
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<para>
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<function>serialize</function> returns a string containing a
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byte-stream representation of any value that can be stored in
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PHP. <function>unserialize</function> can use this string to
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recreate the original variable values. Using serialize to
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save an object will save all variables in an object. The
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methods in an object will not be saved, only the name of
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the class.
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</para>
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<para>
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In order to be able to <function>unserialize</function> an object, the
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class of that object needs to be defined. That is, if you have an object
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of class A and serialize this, you'll
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get a string that refers to class A and contains all values of variables
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contained in it. If you want to be able to unserialize
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this in another file, an object of class A, the
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definition of class A must be present in that file first.
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This can be done for example by storing the class definition of class A
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in an include file and including this file or making use of the
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<function>spl_autoload_register</function> function.
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</para>
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<informalexample>
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<programlisting role="php">
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<![CDATA[
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<?php
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// classa.inc:
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class A {
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public $one = 1;
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public function show_one() {
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echo $this->one;
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}
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}
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// page1.php:
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include("classa.inc");
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$a = new A;
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$s = serialize($a);
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// store $s somewhere where page2.php can find it.
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file_put_contents('store', $s);
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// page2.php:
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// this is needed for the unserialize to work properly.
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include("classa.inc");
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$s = file_get_contents('store');
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$a = unserialize($s);
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// now use the function show_one() of the $a object.
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$a->show_one();
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?>
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]]>
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</programlisting>
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</informalexample>
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<para>
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If an application is using sessions and uses
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<function>session_register</function> to register objects, these objects
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are serialized automatically at the end of each PHP page, and are
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unserialized automatically on each of the following pages. This means that
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these objects can show up on any of the application's pages once they become
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part of the session. However, the <function>session_register</function> is
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removed since PHP 5.4.0.
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</para>
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<para>
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It is strongly recommended that if an application serializes objects, for use
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later in the application, that the application includes the class definition
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for that object throughout the application. Not doing so might result in an
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object being unserialized without a class definition, which will result in
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PHP giving the object a class of <classname>__PHP_Incomplete_Class_Name</classname>,
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which has no methods and would render the object useless.
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</para>
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<para>
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So if in the example above <varname>$a</varname> became part of a session
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by running <literal>session_register("a")</literal>, you should include the
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file <literal>classa.inc</literal> on all of your pages, not only <filename>page1.php</filename>
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and <filename>page2.php</filename>.
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</para>
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<para>
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Beyond the above advice, note that you can also hook into the serialization
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and unserialization events on an object using the
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<link linkend="object.sleep">__sleep()</link> and
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<link linkend="object.wakeup">__wakeup()</link> methods. Using
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<link linkend="object.sleep">__sleep()</link> also allows you to only
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serialize a subset of the object's properties.
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</para>
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</sect1>
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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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