title: Interfaces and abstract class inheritance, implementation in extended classes
body: <p>In every example I've seen, extended classes implement the interfaces of their parents. For reference, the following example:</p>
  
  <pre><code>interface MyInterface{
      public function foo();
      public function bar();
  }
  
  abstract class MyAbstract implements MyInterface{
      public function foo(){ /* stuff */ }
      public function bar(){ /* stuff */ }
  }
  
  // what i usually see
  class MyClass extends MyAbstract implements MyInterface{}
  
  // what i'm curious about
  class MyOtherClass extends MyAbstract{}
  </code></pre>
  
  <p>Is failure to implement an interface in a child, which is implemented by a parent, considered bad practice or something? Are there any technical drawbacks to omitting the implementation in the child? </p>