(PHP 5 >= 5.1.0, PHP 7, PHP 8)
array_diff_ukey — Computes the difference of arrays using a callback function on the keys for comparison
   Compares the keys from array against the keys
   from arrays and returns the difference.
   This function is like array_diff() except the
   comparison is done on the keys instead of the values.
  
Unlike array_diff_key() a user supplied callback function is used for the indices comparison, not internal function.
arrayThe array to compare from
arraysArrays to compare against
key_compare_funcLa funzione di confronto deve restituire un intero minore, uguale o maggiore di zero se il primo argomento è considerato essere minore, uguale o maggiore del secondo.
   Returns an array containing all the entries from
   array that are not present in any of the other arrays.
  
Example #1 array_diff_ukey() example
<?php
function key_compare_func($key1, $key2)
{
    if ($key1 == $key2)
        return 0;
    else if ($key1 > $key2)
        return 1;
    else
        return -1;
}
$array1 = array('blue'  => 1, 'red'  => 2, 'green'  => 3, 'purple' => 4);
$array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan'   => 8);
var_dump(array_diff_ukey($array1, $array2, 'key_compare_func'));
?>Il precedente esempio visualizzerà:
array(2) {
  ["red"]=>
  int(2)
  ["purple"]=>
  int(4)
}
Nota:
This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using
array_diff_ukey($array1[0], $array2[0], 'callback_func');.
