title: How do you add abstract class library in the Codeigniter framework?
body: <p>I have the following code in file called <code>AbstractClass.php</code> in the <code>libraries</code> folder </p>
  
  <pre><code>abstract class AbstractClass {
    abstract protected doSomething ();
  }
  
  class ConcreteClass extends AbstractClass {
    public function doSomething () {};
  
  }
  </code></pre>
  
  <p>When I try to load the <code>AbstractClass</code> from <code>controllers</code> as follows:</p>
  
  <pre><code>$this-&gt;load-&gt;library('AbstractClass');
  </code></pre>
  
  <p>I get <code>Unable to load the requested class: AbstractClass</code> error.</p>
  
  <p>What am I doing wrong? Should I just include the file rather than loading it?</p>
  
  <p>Thanks</p>