yiisoft/yii2 — pull request #4154 by Alex-Code (2014-07-01 13:15:05+00:00)
Title: Use array_replace_recursive instead of array_merge

Use ```array_replace_recursive``` instead of ```array_merge``` for ```$config```

e.g.
I had this in with the config to set the ```ActiveField``` class for forms.
```
Yii::$container->set('yii\bootstrap\ActiveForm', [
'fieldConfig' => [
'class' => 'common\components\ActiveField',
],
]);
```

When using the form I wanted to change some css classes.
```
'horizontal',
'fieldConfig' => [
'horizontalCssClasses' => [
'label' => 'col-sm-2',
'wrapper' => 'col-sm-8',
'hint' => 'col-sm-2'
]
]
]) ?>
```
This would overwrite the initial config falling back to the default ```ActiveField``` class

If it's OK I will update the changelog.