PHP function array_diff(array $array1, array $array2, array ...$_) int[]
------------------------------------------------------------------------  
Computes the difference of arrays
  
Parameters:
array--$array1--The array to compare from
array--$array2--An array to compare against
array--...$_--[optional]
  
Returns:an array containing all the entries from array1 that are not present in any of the other arrays.