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   1 ---
   2 title: Class inheritance or Containers?
   3 author: m6w6
   4 tags:
   5 - PHP
   6 ---
   7
   8 While talking with Daniel and Lorenzo about "Tree Reincarnated" I regularly
   9 stumble across the question what approach to use to implement different
  10 backends: **"Class inheritance or Containers?"**.
  11
  12 I personally feel that using the container approach leads to massive code
  13 duplication, while using class inheritance avoids the most (_most_, because
  14 there's no real multiple class inheritance in PHP).
  15
  16 ## Container
  17 ```php
  18     class PublicAPI
  19     {
  20         var $container; // SpecificAPI
  21
  22         function doSomething()
  23         {
  24             return $this->container->doSomething();
  25         }
  26     }
  27 ```
  28
  29 ## Class Inheritance
  30
  31 ```php
  32     class SpecificAPI extends PublicAPI
  33     {
  34         function doSomething()
  35         {
  36             // do something only this class needs to do
  37         }
  38     }
  39     ?>
  40 ```
  41
  42 So what do you feel about this topic and how you'd handle that?
  43
  44 ## UPDATE
  45
  46 While looking again at Daniel's [nice diagram](http://devel.webcluster.at/~daniel/pear/Tree/docs/Tree.png?),
  47 I feel like we've already reached the point where solving this problem with class
  48 inheritence is impossible (despite using aggregate*() - you're right Lorenzo,
  49 again :) have nice holidays! ).
  50
  51 Tree_Admin_Simple_MDB2 would have to extend Tree_Simple_MDB2 **and**
  52 Tree_Admin_Simple_RDBMS...
  53
  54 Mike's arrived at the dead end, again ;)