Using PHP's array_diff() Function to Compute Array Differences

In PHP, the array_diff() function is a useful tool for computing the difference between arrays. It takes two or more arrays and returns a new array containing the values from the first array that are not present in any of the other arrays.

Syntax

array_diff(array1, array2, array3, ...)

Parameters

array1 : The first array to compare (required).

array2 : The second array to compare (required).

array3, ... : Additional arrays to compare (optional).

Return Value

Returns a new array containing the values from array1 that are not present in any of the other arrays.

Examples

Example 1

$array1 = array("apple", "banana", "orange", "grape");
$array2 = array("banana", "grape", "pear");
$result = array_diff($array1, $array2);
print_r($result);

Output:

Array
(
    [0] => apple
    [2] => orange
)

This shows that "apple" and "orange" are not found in $array2.

Example 2

$array1 = array(1, 2, 3, 4, 5);
$array2 = array(2, 3, 6);
$result = array_diff($array1, $array2);
print_r($result);

Output:

Array
(
    [0] => 1
    [3] => 4
    [4] => 5
)

Values 1, 4, and 5 are not present in $array2.

Example 3

$array1 = array("a" => "apple", "b" => "banana", "c" => "orange");
$array2 = array("a" => "apple", "b" => "pear");
$result = array_diff($array1, $array2);
print_r($result);

Output:

Array
(
    [c] => orange
)

The element with key "c" ("orange") does not exist in $array2.

Summary

The array_diff() function is a practical PHP function for calculating array differences. By comparing multiple arrays, you can identify elements that are unique to the first array.