title: How to set value in array helper Yii2?
body: <p>I want to set value of array helper in Yii 2 as id (primary key of database).
  But when I use it shows me 0,1,2,3,.. not its real id number.</p>
  
  <p>Here is my array helper code:</p>
  
  <pre><code>&lt;?= Html::activeDropDownList($model, 'username',
    array_merge(array(''=&gt;' '), ArrayHelper::map(Experts::find()-&gt;all(), 'id', 'username'))) ?&gt;
  </code></pre>
  
  <p>How can I access real value of primary id??</p>
  
  <p>When I use other parameter it works correctly but when I use id it shows number from 0 to up : | </p>