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Singleton class scope problem

On my site I want to make two classes. One that can be instantiated
normally and one with extended functionality that can only be
instantiated once. The Singleton pattern thus seems like a logical
choice for the second class. However, I would like the second
(singleton) class to extend the first. Something like this:
<?php
class User
{
public function __construct ()
{
doSomething();
}
}

class Member extends User
{
private static $instance = NULL;
public static function getInstance ()
{
if (self::$instanc e === NULL)
self::$instance = new Member;
return self::$instance ;
}

private function __construct () {}
private function __clone () {}
}
?>
But this gives me the following error:
Fatal error: Access level to Member::__const ruct() must be public (as
in class User) in class.member.ph p on line 6

But I don't want the constructor to be public, because I want it to be
impossible to create more than one instance.

Does anybody know what to do about this?

Thanks.

Jul 17 '05
10 3024
Oli Filth wrote:
Variables (including class instances and static members) are not
shared between PHP runs.


Totally correct and this is indeed the true meaning of 'thread-safety'.
However, the term is often abused in PHP to indicate shared object access
during a script run as it was introduced into this discussion.
JW

Jul 17 '05 #11

This thread has been closed and replies have been disabled. Please start a new discussion.

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