@qiangxue Also why we should use another logic for DbManager when for example PhpManager:

```
	public function removeItemChild($itemName, $childName)
	{
		if (isset($this->_children[$itemName][$childName])) {
			unset($this->_children[$itemName][$childName]);
			return true;
		} else {
			return false;
		}
	}

```

So if follow your suggestion we need to change this to:

```
	public function removeItemChild($itemName, $childName)
	{
		if (isset($this->_children[$itemName][$childName])) {
			unset($this->_children[$itemName][$childName]);
		}
		return true;
	}

```

This is wrong.