开关关联数组两个项目

例如：

$arr = array(
  'apple'      => 'sweet',
  'grapefruit' => 'bitter',
  'pear'       => 'tasty',
  'banana'     => 'yellow'
);

我想改用柚子，梨的位置，所以，阵列将处于

I want to switch the positions of grapefruit and pear, so the array will become

$arr = array(
  'apple'      => 'sweet',
  'pear'       => 'tasty',
  'grapefruit' => 'bitter',
  'banana'     => 'yellow'
)

我知道我想改用元素的键和值，有一个简单的方法来做到这一点？还是会需要一个循环+创建新阵列？

I know the keys and values of the elements I want to switch, is there an easy way to do this? Or will it require a loop + creating a new array?

感谢