title: Check in PHP 7.4 whether a property is really initialized or not
body: <p>I want to check in PHP 7.4 whether a property is really initialized or not. Setting the property to null means it is initialized with null.</p>
  <p>I can not use <code>isset</code> because it returns false even when it is set to null.<br />
  I can not use <code>property_exists</code> because it returns true even when it is not initialized.</p>
  <p>The only way I know is with <code>ReflectionProperty::isInitialized</code>, but that feels a little bit strange, that I need to use this detour.</p>
  <pre><code>class DTO {
      public ?string $something;
  }
  
  $object = new DTO();
  $object-&gt;something = null;
  
  isset($object-&gt;something); //returns false
  is_initialized($object-&gt;something); //should return true;
  </code></pre>
  <p>I could write this function using ReflectionProperty, but maybe I'm missing something?</p>