title: instanceof equivalent for a string-represented classname
body: <p>I'm looking for a functionality, in the example below called &quot;theFunctionILookFor&quot;, that will make the code work.</p>
  <pre><code>$myClassName = &quot;someName&quot;;
  $parentOrInterfaceName = &quot;someParent&quot;;
  if (theFunctionILookFor($myClassName)) {
      echo &quot;is parent&quot;;
  }
  </code></pre>
  <p>Edit: I try to avoid instantiating the class just to perform this check. I would like to be able to pass 2 string parameters to the checking function</p>