The PlayStation Network will be offline for scheduled maintenance from 16:00 (BST) Thursday 24th May until – 08:00 (BST) on Friday 25th May. During the maintenance window, the PlayStation Store will be inaccessible along with other PSN related services like the PlayStation Blog.
If you wish to play online during the maintenance, then you may be able to do so if you sign in to PSN before 16:00 (BST) on Thursday 24th May. During this maintenance, you can continue to collect in-game trophies and these will be updated on your profile once PlayStation Network is back up and running.