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</div><hr /><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 <em class="emphasis">clone</em> keyword (which calls the
object's <a href="language.oop5.cloning.html#object.clone" class="link">__clone()</a> method if possible).
An object's <a href="language.oop5.cloning.html#object.clone" class="link">__clone()</a> method
cannot be called directly.
</p>
<div class="informalexample">
<div class="example-contents">
<div class="cdata"><pre>
$copy_of_object = clone $object;
</pre></div>
</div>
</div>
<p class="para">
When an object is cloned, PHP 5 will perform a shallow copy of all of the
object's properties. Any properties that are references to other variables,
will remain references.
</p>
<div class="methodsynopsis dc-description" id="object.clone">
<span class="type"><span class="type void">void</span></span> <span class="methodname"><strong>__clone</strong></span>
( <span class="methodparam">void</span>
)</div>
<p class="para">
Once the cloning is complete, if a <a href="language.oop5.cloning.html#object.clone" class="link">__clone()</a> method is defined, then
the newly created object's <a href="language.oop5.cloning.html#object.clone" class="link">__clone()</a> method will be called, to allow any
necessary properties that need to be changed.
</p>
<div class="example" id="example-225">
<p><strong>Example #1 Cloning an object</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">SubObject<br /></span><span style="color: #007700">{<br /> static </span><span style="color: #0000BB">$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"><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>
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