mirror of
https://github.com/sigmasternchen/php-doc-en
synced 2025-03-18 18:08:54 +00:00
1ac85b8934
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@163048 c90b9560-bf6c-de11-be94-00142212c4b1
113 lines
3.1 KiB
XML
113 lines
3.1 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
|
|
<!-- $Revision: 1.1 $ -->
|
|
<sect1 id="language.oop5.decon">
|
|
<title>Constructors and Destructors</title>
|
|
<sect2 id="oop5-decon-constructor">
|
|
<title>Constructor</title>
|
|
<para>
|
|
PHP 5 allows developers to declare constructor methods for classes.
|
|
Classes which have a constructor method call this method on each
|
|
newly-created object, so it is suitable for any initialization that the
|
|
object may need before it is used.
|
|
</para>
|
|
<note>
|
|
<simpara>
|
|
Parent constructors are not called implicitly. In order to run
|
|
a parent constructor, a call to
|
|
<function>parent::__construct</function> is required.
|
|
</simpara>
|
|
</note>
|
|
<example>
|
|
<title>using new unified constructors</title>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
class BaseClass {
|
|
function __construct() {
|
|
print "In BaseClass constructor\n";
|
|
}
|
|
}
|
|
|
|
class SubClass extends BaseClass {
|
|
function __construct() {
|
|
parent::__construct();
|
|
print "In SubClass constructor\n";
|
|
}
|
|
}
|
|
|
|
$obj = new BaseClass();
|
|
$obj = new SubClass();
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
</example>
|
|
<para>
|
|
For backwards compatibility, if PHP 5 cannot find a
|
|
<function>__construct</function> function for a given class, it will
|
|
search for the old-style constructor function, by the name of the class.
|
|
Effectively, it means that the only case that would have compatibility
|
|
issues is if the class had a method named
|
|
<function>__construct</function> which was used for different semantics.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="oop5-decon-destructor">
|
|
<title>Destructor</title>
|
|
<para>
|
|
PHP 5 introduces a destructor concept similar to that of other
|
|
object-oriented languages, such as Java: When the last reference to an
|
|
object is destroyed the object's destructor, which is a class method
|
|
named <function>__destruct</function> that receives no parameters, is
|
|
called before the object is freed from memory.
|
|
</para>
|
|
<example>
|
|
<title>Destructor Example</title>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
class MyDestructableClass {
|
|
function __construct() {
|
|
print "In constructor\n";
|
|
$this->name = "MyDestructableClass";
|
|
}
|
|
|
|
function __destruct() {
|
|
print "Destroying " . $this->name . "\n";
|
|
}
|
|
}
|
|
|
|
$obj = new MyDestructableClass();
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
</example>
|
|
<para>
|
|
Like constructors, parent destructors will not be called implicitly by
|
|
the engine. In order to run a parent destructor, one would have to
|
|
explicitly call <function>parent::__destruct</function> in the destructor
|
|
body.
|
|
</para>
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
<!-- Keep this comment at the end of the file
|
|
Local variables:
|
|
mode: sgml
|
|
sgml-omittag:t
|
|
sgml-shorttag:t
|
|
sgml-minimize-attributes:nil
|
|
sgml-always-quote-attributes:t
|
|
sgml-indent-step:1
|
|
sgml-indent-data:t
|
|
indent-tabs-mode:nil
|
|
sgml-parent-document:nil
|
|
sgml-default-dtd-file:"../../manual.ced"
|
|
sgml-exposed-tags:nil
|
|
sgml-local-catalogs:nil
|
|
sgml-local-ecat-files:nil
|
|
End:
|
|
vim600: syn=xml fen fdm=syntax fdl=2 si
|
|
vim: et tw=78 syn=sgml
|
|
vi: ts=1 sw=1
|
|
-->
|