如何更新数组值然后使用PHP将其存储/保存在数组中？

I am operating with array that looks like this:

$pms = array(
    'msg1' => array(
        'status' => 'unread',
        'subject' => 'bla bla'
    ),
    'msg2' => array(
        'status' => 'unread',
        'subject' => 'test..'
    ),
    'msg3' => array(
        'status' => 'unread',
        'subject' => 'moreee..'
    )
);

What I want to achieve is to be able to select 'msg3' for example, update the status from 'unread' to 'read' and put it back in its position in the array.

How to do that?

Just assign the new value to it like any other array variable:

$pms['msg3']['status'] = 'read';