$value = [1, 20, 60, 3, 900, 34, 93, 5, 12, 24, 16, 200]
$mask = [ 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1 ]

##</code><code>##

$a1 = 
[
  [60,30,900]  #from $values
  [2,3,4]      #their original indexes
]
and 
$a2 = 
[
  [5,12,24]
  [7,8,9]
]