Get keys of 5 bigests value from array

Get keys of 5 bigests value from array

I have one problem. I must get 5 images which rates are the biggest. I
have table which key = image_id and value = average rating.
Below is print_r of this array
Array ( ['5'] => 5.00 ['4'] => 3.05 ['12'] => 3.00 ['11'] => 4.00 ['21']
=> 2.11 ['53'] => 4.44 )
For example
['5'] => 5.00
means that img which id = '5' have rating 5.00
Expected output 2 Arrays ($id and $rating)
Array ( [0] => '5' [1] => '53' [2] => '11' [3] => '4' [4] => '12' )
Array ( [0] => '5.00' [1] => '4.44' [2] => '4.00' [3] => '3.05' [4] =>
'3.00' )
Can you help me in this?