Source of: /manual/en/language.oop5.cloning.php
<?php
include_once $_SERVER['DOCUMENT_ROOT'] . '/include/shared-manual.inc';
$TOC = array();
$PARENTS = array();
include_once dirname(__FILE__) ."/toc/language.oop5.inc";
$setup = array (
'home' =>
array (
0 => 'index.php',
1 => 'PHP Manual',
),
'head' =>
array (
0 => 'UTF-8',
1 => 'en',
),
'this' =>
array (
0 => 'language.oop5.cloning.php',
1 => 'Object Cloning',
),
'up' =>
array (
0 => 'language.oop5.php',
1 => 'Classes and Objects',
),
'prev' =>
array (
0 => 'language.oop5.final.php',
1 => 'Final Keyword',
),
'next' =>
array (
0 => 'language.oop5.object-comparison.php',
1 => 'Comparing Objects',
),
);
$setup["toc"] = $TOC;
$setup["parents"] = $PARENTS;
manual_setup($setup);
manual_header();
?>
<div id="language.oop5.cloning" class="sect1">
<h2 class="title">Object Cloning</h2>
<p class="para">
Creating a copy of an object with fully replicated properties is not
always the wanted behavior. A good example of the need for copy
constructors, is if you have an object which represents a GTK window and the
object holds the resource of this GTK window, when you create a duplicate
you might want to create a new window with the same properties and have the
new object hold the resource of the new window. Another example is if your
object holds a reference to another object which it uses and when you
replicate the parent object you want to create a new instance of this other
object so that the replica has its own separate copy.
</p>
<p class="para">
An object copy is created by using the clone keyword (which calls the
object's __clone() method if possible). An object's __clone() method
cannot be called directly.
</p>
<div class="informalexample">
<div class="example-contents programlisting">
<div class="cdata"><pre>
$copy_of_object = clone $object;
</pre></div>
</div>
</div>
<p class="para">
When an object is cloned, PHP 5 will perform a shallow copy of all of the
object's properties. Any properties that are references to other variables,
will remain references.
</p>
<p class="para">
Once the cloning is complete, if a __clone() method is defined, then
the newly created object's __clone() method will be called, to allow any
necessary properties that need to be changed.
</p>
<div class="example">
<p><b>Example #1 Cloning an object</b></p>
<div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">SubObject<br /></span><span style="color: #007700">{<br /> static </span><span style="color: #0000BB">$instances </span><span style="color: #007700">= </span><span style="color: #0000BB">0</span><span style="color: #007700">;<br /> public </span><span style="color: #0000BB">$instance</span><span style="color: #007700">;<br /><br /> public function </span><span style="color: #0000BB">__construct</span><span style="color: #007700">() {<br /> </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">instance </span><span style="color: #007700">= ++</span><span style="color: #0000BB">self</span><span style="color: #007700">::</span><span style="color: #0000BB">$instances</span><span style="color: #007700">;<br /> }<br /><br /> public function </span><span style="color: #0000BB">__clone</span><span style="color: #007700">() {<br /> </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">instance </span><span style="color: #007700">= ++</span><span style="color: #0000BB">self</span><span style="color: #007700">::</span><span style="color: #0000BB">$instances</span><span style="color: #007700">;<br /> }<br />}<br /><br />class </span><span style="color: #0000BB">MyCloneable<br /></span><span style="color: #007700">{<br /> public </span><span style="color: #0000BB">$object1</span><span style="color: #007700">;<br /> public </span><span style="color: #0000BB">$object2</span><span style="color: #007700">;<br /><br /> function </span><span style="color: #0000BB">__clone</span><span style="color: #007700">()<br /> {<br /> </span><span style="color: #FF8000">// Force a copy of this->object, otherwise<br /> // it will point to same object.<br /> </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">object1 </span><span style="color: #007700">= clone </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">object1</span><span style="color: #007700">;<br /> }<br />}<br /><br /></span><span style="color: #0000BB">$obj </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyCloneable</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">$obj</span><span style="color: #007700">-></span><span style="color: #0000BB">object1 </span><span style="color: #007700">= new </span><span style="color: #0000BB">SubObject</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">$obj</span><span style="color: #007700">-></span><span style="color: #0000BB">object2 </span><span style="color: #007700">= new </span><span style="color: #0000BB">SubObject</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">$obj2 </span><span style="color: #007700">= clone </span><span style="color: #0000BB">$obj</span><span style="color: #007700">;<br /><br /><br />print(</span><span style="color: #DD0000">"Original Object:\n"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">);<br /><br />print(</span><span style="color: #DD0000">"Cloned Object:\n"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$obj2</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents para"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Original Object:
MyCloneable Object
(
[object1] => SubObject Object
(
[instance] => 1
)
[object2] => SubObject Object
(
[instance] => 2
)
)
Cloned Object:
MyCloneable Object
(
[object1] => SubObject Object
(
[instance] => 3
)
[object2] => SubObject Object
(
[instance] => 2
)
)
</pre></div>
</div>
</div>
</div><?php manual_footer(); ?>
