array_diff_ukey : Difference between two or more arrays by comparing keys by using callback function

This function takes two or more arrays as input and then returns the result array as difference.

$new_array = array_diff_ukey ($array1, $array2,....,my_function());

my_function() : is the callback function to return integer less than , equal to or greater than zero after comparing the keys.

Returns all elements of $array1 which are not present in $array2 considering keys. Keys comparison is done through call-back function my_function().

Example with two arrays

function my_function($a, $b)
{
    if ($a === $b) {
        return 0;
    }
    return ($a > $b)? 1:-1;
}

$first=array('One' =>'First','Two'=>'Second','Three'=>'Third','Fourth');
$second=array('One'=> 'First','Fourth','2nd');

$result=array_diff_ukey($first,$second,"my_function");
while (list ($key, $val) = each ($result)) {
echo "$key -> $val <br>";
}

Output is here.

Two -> Second 
Three -> Third

Keys of the first index are retained. ( no re-indexing done here) . The element with value Third is included in output as the index or key is not matching with $second array though the value is matching.

Example 2

function my_function($a, $b) {
    static $match = [
        'First' => 'One',
        'Second' => 'Two',
        'Third' => 'Three',
        'Fourth' => 'Four',
        'Fifth' => 'five'
    ];
    if (isset($match[$a])) {
        return $match[$a] != $b;
    } elseif(isset($match[$b])) {
        return $match[$b] != $a; 
    }
    return true; 
// 0 returned if there is a match and 1 if no match 
}

$first=array('First' =>1,'Second'=>2,'Third'=>33,'FourthH'=>4,'Fifth'=>5);
$second=array('One'=>1,'Two'=>2,'Three'=>3,'Four'=>4);
$result=array_diff_ukey($first,$second,"my_function");
while (list ($key, $val) = each ($result)) {
echo "$key -> $val <br>";
}

Output is here

FourthH -> 4 
Fifth -> 5

The function my_function() checks the entries and returns 0 if there is a match and returns 1 if no match is found.
We are comparing keys only ( not values ) so Third =>33 is matched with Three=>3 so it not appearing in output (as the difference only shown). Similarly FourthH=>4 is not matched with Four=>4 as index or key is compared ( which is not matching ) though the value 4 is matching. Hence it is included in the output.

Example 2: Case-Insensitive Key Comparison

You can use array_diff_ukey() to perform case-insensitive key comparison by defining a custom comparison function:

$arr1 = array("Key1" => 1, "Key2" => 2);
$arr2 = array("key1" => 1, "key3" => 3);

function caseInsensitiveCompare($key1, $key2) {
    return strcasecmp($key1, $key2);
}

$result = array_diff_ukey($arr1, $arr2, "caseInsensitiveCompare");
print_r($result); // Outputs: Array ( [Key2] => 2 )

Difference between arrays considering values
Array REFERENCE

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

About the author Watch on YouTube

Connect:

Subscribe to our YouTube Channel here

array_diff_ukey(): Difference between two arrays comparing keys through callback function

Example with two arrays

Example 2

Example 2: Case-Insensitive Key Comparison

Subhendu Mohapatra