array_diff_ukey in PHP

The PHP array_diff_ukey() function compares the keys in two or more arrays, checking for differences, before comparing the keys in a user-defined function, then returns an array with the keys and values from the first array, if the function allows it.

Syntax:

array_diff_ukey(array1,array2,array3...,function)

array1 : Required. The first array is the array that the others will be compared with
array2 : Required. An array to be compared with the first array
array3 : Optional. An array to be compared with the first array

function : Required. The name of the user-made function
Tip: You can compare the first array with one array, or as many as you like.
Note: Only the keys have to be the same to get a match, both in the automatic comparison and in the user-defined function.

Example:

<?php
function myfunc($par1,$par2)
{
if($par1===$par2)
{
 return 0;
}
if($par1>$par2)
{
 return 1;
}
else
{
 return -1;
}
}
$daysarr1 = array(0=>"Sunday",1=>"Monday",2=>"Tuesday");
$daysarr2 = array(3=>"Wednesday",1=>"Friday",5=>"Thursday");
$daysarr3 = array(6=>"Sunday",7=>"Saturday",0=>"Tuesday");
print_r( array_diff_ukey($daysarr1,$daysarr2,$daysarr3,"myfunc") );
?>

O/P:

Array (
          [2] => Tuesday
        )