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Be more clear how __clone() works (bug #27100), and example modifications.

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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@165665 c90b9560-bf6c-de11-be94-00142212c4b1
This commit is contained in:
Curt Zirzow 2004-08-07 17:39:27 +00:00
parent 604ff8ed48
commit c43b87be6a
1 changed files with 74 additions and 24 deletions
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98
language/oop5/cloning.xml
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@ -1,5 +1,5 @@
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.2 $ -->
<!-- $Revision: 1.3 $ -->
<sect1 id="language.oop5.cloning">
<title>Object cloning</title>
@ -30,14 +30,13 @@ $copy_of_object = clone $object;
</informalexample>
<para>
When the developer asks to create a new copy of an object, PHP 5 will check
if a __clone() method has been defined or not. If not, it will call a
default __clone() which will copy all of the object's properties. If a
__clone() method is defined, then it will be responsible to set the
necessary properties in the created object. For convenience, the engine
will supply a function that imports all of the properties from the source
object, so that they can start with a by-value replica of the source
object, and only override properties that need to be changed.
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. 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.
</para>
<example>
@ -45,34 +44,85 @@ $copy_of_object = clone $object;
<programlisting role="php">
<![CDATA[
<?php
class SubObject {
static $instances = 0;
public $instance;
public function __construct() {
$this->instance = ++self::$instances;
}
public function __clone() {
$this->instance = ++self::$instances;
}
}
class MyCloneable {
static $id = 0;
function MyCloneable() {
$this->id = self::$id++;
}
public $object1;
public $object2;
function __clone() {
$this->address = "New York";
$this->id = self::$id++;
}
function __clone() {
// Force a copy of this->object, otherwise
// it will point to same object.
$this->object1 = clone($this->object1);
}
}
$obj = new MyCloneable();
$obj->name = "Hello";
$obj->address = "Tel-Aviv";
$obj->object1 = new SubObject();
$obj->object2 = new SubObject();
print $obj->id . "\n";
$obj2 = clone $obj;
$obj_cloned = clone $obj;
print $obj_cloned->id . "\n";
print $obj_cloned->name . "\n";
print $obj_cloned->address . "\n";
print("Original Object:\n");
print_r($obj);
print("Cloned Object:\n");
print_r($obj2);
?>
]]>
</programlisting>
&example.outputs;
<screen role="php">
<![CDATA[
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
)
)
]]>
</screen>
</example>
</sect1>