PHP array_udiff() Function: Syntax, Parameters, Usage, and Example

array_udiff() is a PHP function used to compare the values of two or more arrays and return the differences. The function accepts the arrays to compare and a callable callback that determines whether two elements are equal. When elements are not equal, array_udiff() adds them to the result array.

Function Syntax

<code>array_udiff(array1, array2, ..., callback)</code>

Function Parameters

array_udiff() accepts three primary parameters:

array1 : the first array to compare.

array2 : the second array to compare.

callback : a user‑defined function that compares two elements and must return an integer greater than, equal to, or less than zero to indicate whether the first argument is greater than, equal to, or less than the second.

Note that array_udiff() can accept multiple arrays as input, but the execution time may increase with the number of arrays provided.

Practical Application Scenarios

array_udiff() is commonly used to find the differences between two arrays and return a new array containing those differing elements. For example, after a data table has been modified, a web application may need to determine which rows have been updated or deleted.

Below is an example that compares two arrays:

<code>$old_array = [1, 2, 3, 4];
$new_array = [2, 4, 6, 8];

$result = array_udiff($old_array, $new_array, function($a, $b) {
    return $a - $b;
});

print_r($result);
</code>

The code above returns an array containing the elements 1 and 3 , which appear in $old_array but not in $new_array .

In PHP development, array_udiff() is a very useful tool for comparing arrays. It helps developers quickly and efficiently identify differences between arrays, saving time and effort. This article aims to deepen readers' understanding of the usage and real‑world applications of array_udiff() .