php man page for array_diff_ukey

ARRAY_DIFF_UKEY(3)							 1							ARRAY_DIFF_UKEY(3)

array_diff_ukey - Computes the difference of arrays using a callback function on the keys for comparison

SYNOPSIS
       array array_diff_ukey (array  $array1, array  $array2, [array  $...], callable  $key_compare_func)

DESCRIPTION
	Compares  the  keys  from $array1 against the keys from $array2 and returns the difference. This function is like array_diff(3) except the
       comparison is done on the keys instead of the values.

	Unlike array_diff_key(3) a user supplied callback function is used for the indices comparison, not internal function.

PARAMETERS
	      o $array1
		- The array to compare from

	      o $array2
		- An array to compare against

	      o $...
		- More arrays to compare against

	      o $key_compare_func
		- The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered	to
		be respectively less than, equal to, or greater than the second.
		int callback (mixed  $a, mixed	$b)

RETURN VALUES
	Returns an array containing all the entries from $array1 that are not present in any of the other arrays.

EXAMPLES
       Example #1

	      array_diff_ukey(3) 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'));
	      ?>

	      The above example will output:

	      array(2) {
		["red"]=>
		int(2)
		["purple"]=>
		int(4)
	      }

NOTES
       Note

	       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');.

SEE ALSO
       array_diff(3), array_udiff(3), array_diff_assoc(3), array_diff_uassoc(3), array_udiff_assoc(3),	array_udiff_uassoc(3),	array_diff_key(3),
       array_intersect(3), array_intersect_assoc(3), array_intersect_uassoc(3), array_intersect_key(3), array_intersect_ukey(3).

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