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</div><hr /><div id="language.oop5.serialization" class="sect1">
<h2 class="title">Object Serialization</h2>
<h2 class="title">Serializing objects - objects in sessions</h2>
<p class="para">
<span class="function"><a href="function.serialize.html" class="function">serialize()</a></span> returns a string containing a
byte-stream representation of any value that can be stored in
PHP. <span class="function"><a href="function.unserialize.html" class="function">unserialize()</a></span> can use this string to
recreate the original variable values. Using serialize to
save an object will save all variables in an object. The
methods in an object will not be saved, only the name of
the class.
</p>
<p class="para">
In order to be able to <span class="function"><a href="function.unserialize.html" class="function">unserialize()</a></span> an object, the
class of that object needs to be defined. That is, if you have an object
of class A and serialize this, you'll
get a string that refers to class A and contains all values of variables
contained in it. If you want to be able to unserialize
this in another file, an object of class A, the
definition of class A must be present in that file first.
This can be done for example by storing the class definition of class A
in an include file and including this file or making use of the
<span class="function"><a href="function.spl-autoload-register.html" class="function">spl_autoload_register()</a></span> function.
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// classa.inc:<br /> <br /> </span><span style="color: #007700">class </span><span style="color: #0000BB">A </span><span style="color: #007700">{<br /> public </span><span style="color: #0000BB">$one </span><span style="color: #007700">= </span><span style="color: #0000BB">1</span><span style="color: #007700">;<br /> <br /> public function </span><span style="color: #0000BB">show_one</span><span style="color: #007700">() {<br /> echo </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">one</span><span style="color: #007700">;<br /> }<br /> }<br /> <br /></span><span style="color: #FF8000">// page1.php:<br /><br /> </span><span style="color: #007700">include(</span><span style="color: #DD0000">"classa.inc"</span><span style="color: #007700">);<br /> <br /> </span><span style="color: #0000BB">$a </span><span style="color: #007700">= new </span><span style="color: #0000BB">A</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$s </span><span style="color: #007700">= </span><span style="color: #0000BB">serialize</span><span style="color: #007700">(</span><span style="color: #0000BB">$a</span><span style="color: #007700">);<br /> </span><span style="color: #FF8000">// store $s somewhere where page2.php can find it.<br /> </span><span style="color: #0000BB">file_put_contents</span><span style="color: #007700">(</span><span style="color: #DD0000">'store'</span><span style="color: #007700">, </span><span style="color: #0000BB">$s</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// page2.php:<br /> <br /> // this is needed for the unserialize to work properly.<br /> </span><span style="color: #007700">include(</span><span style="color: #DD0000">"classa.inc"</span><span style="color: #007700">);<br /><br /> </span><span style="color: #0000BB">$s </span><span style="color: #007700">= </span><span style="color: #0000BB">file_get_contents</span><span style="color: #007700">(</span><span style="color: #DD0000">'store'</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">$a </span><span style="color: #007700">= </span><span style="color: #0000BB">unserialize</span><span style="color: #007700">(</span><span style="color: #0000BB">$s</span><span style="color: #007700">);<br /><br /> </span><span style="color: #FF8000">// now use the function show_one() of the $a object. <br /> </span><span style="color: #0000BB">$a</span><span style="color: #007700">-></span><span style="color: #0000BB">show_one</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
If an application is using sessions and uses
<span class="function"><a href="function.session-register.html" class="function">session_register()</a></span> to register objects, these objects
are serialized automatically at the end of each PHP page, and are
unserialized automatically on each of the following pages. This means that
these objects can show up on any of the application's pages once they become
part of the session. However, the <span class="function"><a href="function.session-register.html" class="function">session_register()</a></span> is
removed since PHP 5.4.0.
</p>
<p class="para">
It is strongly recommended that if an application serializes objects, for use
later in the application, that the application includes the class definition
for that object throughout the application. Not doing so might result in an
object being unserialized without a class definition, which will result in
PHP giving the object a class of <strong class="classname">__PHP_Incomplete_Class_Name</strong>,
which has no methods and would render the object useless.
</p>
<p class="para">
So if in the example above <var class="varname"><var class="varname">$a</var></var> became part of a session
by running <em>session_register("a")</em>, you should include the
file <em>classa.inc</em> on all of your pages, not only <var class="filename">page1.php</var>
and <var class="filename">page2.php</var>.
</p>
<p class="para">
Beyond the above advice, note that you can also hook into the serialization
and unserialization events on an object using the
<a href="language.oop5.magic.html#object.sleep" class="link">__sleep()</a> and
<a href="language.oop5.magic.html#object.wakeup" class="link">__wakeup()</a> methods. Using
<a href="language.oop5.magic.html#object.sleep" class="link">__sleep()</a> also allows you to only
serialize a subset of the object's properties.
</p>
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