title: Binding an array of Instance Types as a parameter for Doctrine DQL
body: <p>Is it possible to bind an array of types to a DQL query for use with <code>INSTANCE OF</code>?</p>
  
  <p>For example, this is the Doctrine DQL for querying an entity by a single specified type.</p>
  
  <pre><code>&lt;?php
  $dql = &lt;&lt;&lt;DQL
  SELECT o FROM \MyProj\AbstractMyObject AS o 
  WHERE o INSTANCE OF :type
  DQL;
  $q = $em-&gt;createQuery($dql);
  $q-&gt;setParameter(
      'type',
      $em-&gt;getClassMetadata(AlphaObject::class);
  );
  $q-&gt;getResult();
  </code></pre>
  
  <p>What is the equivalent method to bind more than one type as a parameter to this query?</p>
  
  <p>The is what I have tried. It doesn't error, but it also does not return any results.</p>
  
  <pre><code>&lt;?php
  $dql = &lt;&lt;&lt;DQL
  SELECT o FROM \MyProj\AbstractMyObject AS o 
  WHERE o INSTANCE OF (:types)
  DQL;
  $q = $em-&gt;createQuery($dql);
  $q-&gt;setParameter(
      'types',
      [
          $em-&gt;getClassMetadata(AlphaObject::class),
          $em-&gt;getClassMetadata(BetaObject::class)
      ]
  );
  $q-&gt;getResult();
  </code></pre>