PHP array diff_ukey() Function

Last Updated : 17 Mar 2025

The array_diff_ukey() is an inbuilt function in PHP. The array_diff_ukey() function compares the keys of two or more arrays with a user-defined function, and returns an array that contains the entries from array1 that are not present in array2 or array3, etc.

This function was introduced in PHP 5.1.

Syntax

Parameter	Description	Is compulsory
array1	The array to compare from	Compulsory
array2	An array to compare against	Compulsory
array3	More arrays to compare against	Optional
User defined function	A string that define a callable comparison function.	Compulsory

Return Type

It returns an array containing all the entries from array1 that are not present in any of the other arrays.

Example 1

<?php
function compfunction($x,$y)
{
if ($x===$y)
{
return 0;
}
return ($x>$y)?1:-1;
}
$comp1=array("a"=>"1","b"=>"2","c"=>"3","j"=>"phptpoint.com");
$comp2=array("a"=>"1","b"=>"2","e"=>"5");
$res=array_diff_ukey($comp1,$comp2,"compfunction");
print_r($res);
?>

Output:

Array(  [c] => 3   [j] => phptpoint.com )

Example 2

<?php
function myfunction($x,$y)
{
if ($x===$y)
{
 return 0;
 }
 return ($x>$y)?1:-1;
}
$alpha1=array("a"=>"apple","b"=>"ball","c"=>"cat");
$alpha2=array("a"=>"ant","b"=>"boy","d"=>"dog");
$alpha3=array("e"=>"elephant","f"=>"fox","a"=>"about");
$result=array_diff_ukey($alpha1,$alpha2,$alpha3,"myfunction");
print_r($result);
?>

Output:

Array ( [c] => cat )

Example 3

<?php
function keyFunction($x, $y)
{
 if ($x === $y) 
{
 return 0;
 }
return ($x > $y) ? 1 : -1;
}
 $lang1 = array(  "a" => "Python",   "b" => "PHP",   "c" => "php" );
$lang2 = array(  "a" => "php",   "b" => "Ruby",  "d" => "php" );
$result = array_diff_ukey($lang1, $lang2, "keyFunction");
print_r($result);
?>

Output:

Array(  [c] => php  )

Example 4

<?php
function compfunction($x, $y)
{
 if ($x === $y) 
{
return 0;
 }
return ($x > $y) ? 1 : -1;
}
 

$game1 = array(  "x" => "cricket",  "y" => "tennis",  "z" => "football" );
$game2 = array( "x" => "golf",  "y" => "hockey",  "w" => "cycling" );
$game3 = array( "u" => "badminton",  "v" => "shooting", "x" => "boxing" );
 $result = array_diff_ukey($game1, $game2, $game3, "compfunction");
print_r($result);
?>

Output:

Array(  [z] => football )

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