Yii2 QueryBuilder union not working - yii2

Question

Here is my code. I want to select results from two columns into one. Thanks.
$messages = (new \yii\db\Query())
->select(['idsender as idotherguy'])
->from('messages')
->where(['idreceiver' => Yii::$app->user->identity->id])
->all();
$messages2 = (new \yii\db\Query())
->select(['idreceiver as idotherguy'])
->from('messages')
->where(['idsender' => Yii::$app->user->identity->id])
->all();
$messages->union($messages2);
after advice here I also tried....
$messages = (new \yii\db\Query())
->select(['idsender as idotherguy'])
->from('messages')
->where(['idreceiver' => Yii::$app->user->identity->id]);
$messages2 = (new \yii\db\Query())
->select(['idreceiver '])
->from('messages')
->where(['idsender' => Yii::$app->user->identity->id]);
$messages->union($messages2);
$messages->all();
and i get query object
yii\db\Query Object
(
[select] => Array
(
[0] => idsender as idotherguy
)
[selectOption] =>
[distinct] =>
[from] => Array
(
[0] => messages
)
[groupBy] =>
[join] =>
[having] =>
[union] => Array
(
[0] => Array
(
[query] => yii\db\Query Object
(
[select] => Array
(
[0] => idreceiver as idotherguy
)
[selectOption] =>
[distinct] =>
[from] => Array
(
[0] => messages
)
[groupBy] =>
[join] =>
[having] =>
[union] =>
[params] => Array
(
)
[_events:yii\base\Component:private] => Array
(
)
[_behaviors:yii\base\Component:private] =>
[where] => Array
(
[idsender] => 2
)
[limit] =>
[offset] =>
[orderBy] =>
[indexBy] =>
[emulateExecution] =>
)
[all] =>
)
)
[params] => Array
(
)
[_events:yii\base\Component:private] => Array
(
)
[_behaviors:yii\base\Component:private] =>
[where] => Array
(
[idreceiver] => 2
)
[limit] =>
[offset] =>
[orderBy] =>
[indexBy] =>
[emulateExecution] =>
)
that is it... I tried also answe bellow and used in select 'idreceiver as idotherguy' ... but the result is the same

Answer 1

you should avoid the alias in united query , use literal select format and apply all to the result only
$messages = (new \yii\db\Query())
->select('idsender as idotherguy')
->from('messages')
->where(['idreceiver' => Yii::$app->user->identity->id]);
$messages2 = (new \yii\db\Query())
->select('idreceiver')
->from('messages')
->where(['idsender' => Yii::$app->user->identity->id]);
$messages->union($messages2);
$messages->all();
for see the result you should
foreach($messages as $key=> $value) {
echo $value->idotherguy;
}
or if the result is an array
foreach($messages as $key=> $value) {
echo $value['idotherguy'];
}
try check the ral sql code this way (instead of $messages->all();)
var_dump( $messages->createCommand()->sql);

Answer 2

Take a look at the documentation http://www.yiiframework.com/doc-2.0/guide-db-query-builder.html#union, you shouldn't have all() in your queries
$messages = (new \yii\db\Query())
->select(['idsender as idotherguy'])
->from('messages')
->where(['idreceiver' => Yii::$app->user->identity->id]);
$messages2 = (new \yii\db\Query())
->select(['idreceiver as idotherguy'])
->from('messages')
->where(['idsender' => Yii::$app->user->identity->id]);
$messages->union($messages2);
$messages->all();

Answer 3

I changed the code offered here like this and it works now fine....
$messages = (new \yii\db\Query())
->select(['idsender as idotherguy'])
->from('messages')
->where(['idreceiver' => Yii::$app->user->identity->id]);
$messages2 = (new \yii\db\Query())
->select(['idreceiver as idotherguy'])
->from('messages')
->where(['idsender' => Yii::$app->user->identity->id]);
$messages = $messages->union($messages2)
->all();
The result now is array with values as I wanted.
Array
(
[0] => Array
(
[idotherguy] => 3
)
[1] => Array
(
[idotherguy] => 11
)
[2] => Array
(
[idotherguy] => 10
)
)
Thanks for help boys :)