title: Codeigniter - Check if a database connection has been configured
body: <p>I have codeigniter configured to use multiple databases. For some customers, we need to query an additional database so this is a matter of:</p>
  
  <pre><code>if( isConfigured(database) )
      foo();
  </code></pre>
  
  <p>However, the attempts I have made have either given the same result whether or not the db is configured in <code>databases.php</code>, or throws an error.</p>
  
  <p>I have attempted the following:</p>
  
  <pre><code>if( $this-&gt;load-&gt;database('optional') == FALSE )
  </code></pre>
  
  <p>Which raises the error <code>You have specified an invalid database connection group</code></p>
  
  <pre><code>try( $this-&gt;load-&gt;database('optional') )
  {
      foo();
  }
  catch(Exception $e)
  {
       doNothing();
  }
  </code></pre>
  
  <p>Which raises the same error</p>
  
  <p>The documentation states that <code>$this-&gt;load-&gt;database('optional', TRUE)</code> returns the connection ID however I cannot check this as the code errors out before returning a value.</p>
  
  <p>I was expecting to be able to check whether or not a property had been set, e.g. <code>$this-&gt;config-&gt;item('db')['optional']</code> but this would be largely guesswork to determine how to access the correct property</p>
  
  <p>I have also looked into the <code>dbutil</code> class but this only applies to databases which have already established a connection.</p>