array_udiff(): Difference between two arrays comparing values through callback function

$new_array = array_udiff ($array1, $array2,....,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','2nd','Third');

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

Two -> Second 
0 -> Fourth  

Example 2: Comparing Multi-dimensional Arrays

We can use array_udiff() with multi-dimensional arrays to find differences between arrays based on specific keys:

function compare_arrays($a, $b) {
    return strcmp($a['name'], $b['name']);
}

$array1 = [
    ['name' => 'John', 'age' => 25],
    ['name' => 'Alice', 'age' => 30]
];
$array2 = [
    ['name' => 'John', 'age' => 27],
    ['name' => 'Bob', 'age' => 35]
];

$result = array_udiff($array1, $array2, 'compare_arrays');
print_r($result);

Example 3: Ignoring Case Sensitivity During Comparison

To compare arrays while ignoring case, use strcasecmp() in the callback:

function compare_ignore_case($a, $b) {
    return strcasecmp($a, $b);
}

$array1 = ['First', 'Second', 'third'];
$array2 = ['first', 'Second', 'Third'];

$result = array_udiff($array1, $array2, 'compare_ignore_case');
print_r($result);

Use Case: Finding Unique Objects in Arrays

By comparing object properties, we can find unique objects across arrays:

class Person {
    public $name;
    public function __construct($name) {
        $this->name = $name;
    }
}

function compare_objects($a, $b) {
    return strcmp($a->name, $b->name);
}

$array1 = [new Person('John'), new Person('Alice')];
$array2 = [new Person('John'), new Person('Bob')];

$result = array_udiff($array1, $array2, 'compare_objects');
print_r($result);

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.

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