((PHP5))

I wanted to dynamically choose an extender for a class.  This took awhile of playing with it but I came up with a solution.  Note that I can't verify how safe it is, but it appears to work for me.  Perhaps someone else can shed light on the details:

<?php

class A { var $value = "Class A\n"; }
class B { var $value = "Class B\n"; }

// Uncomment which extender you want.  You can use variables as well.
// define('__EXTENDER__', 'A');
   define('__EXTENDER__', 'B');

// Use eval to create a wrapper class.
eval('class EXTENDER extends '. __EXTENDER__ . ' { }');

class C extends EXTENDER
{
  function __construct()
  {
     echo $this->value;
  }
}

$t = new C;

?>

Outputs:   Class B

Practical application:  I have a database abstraction system that has individual classes for mysql, pgsql, et al.  I want to be able to create a global db class that extends one of the individual db classes depending on the application configuration.

I know that there are probably much better ways of doing this but I haven't reached that level when it comes to classes.