将数组的php数组转换为单个数组

我有一个数组，其值都是特定格式的数组，如下所示:

I have an array whose values are all arrays of a specific format that looks like this:

Array
(
    [0] => Array
           (
               [username] => John
           )    
    [1] => Array
           (
               [username] => Joe
           )
    [2] => Array
           (
               [username] => Jake
           )
)

我想要这个:

Array
(
    [0] => John   
    [1] => Joe
    [2] => Jake
)

我可以使用循环手动执行此操作，但有更好的方法吗?如果不是，是否可以对具有公共属性的对象数组执行此操作?

I can do this manually with a loop but is there a better way? If not, is it possible to do this for an array of objects that have a common attribute?