How to use array_filter() Function In PHP

The array_filter() function filters elements of an array using a callback function. If all elements pass the filter (i.e., are equal to the first element), the filtered array will have the same number of elements as the original array.

Example: This example shows the use of the above-mentioned appraoch.

PHP

<?php

function isAllEqual($arr) {
    $val = reset($arr);
    
    return count(array_filter($arr, 
        function($item) use ($val) {
            return $item === $val;
        })) === count($arr);
}

// Driver code
$arr1 = [1, 1, 1, 1];
$arr2 = [4, 2, 3, 4];

echo isAllEqual($arr1) 
    ? "All values are equal\n" 
    : "Values are not equal\n";

echo isAllEqual($arr2) 
    ? "All values are equal." 
    : "Values are not equal.";

?>

Output

All values are equal
Values are not equal.

Explanation:

reset($array) gets the first value of the array.
array_filter($array, $callback) returns an array of elements that pass the filter.
The callback checks if each element is equal to the first value.
The filtered array should have the same length as the original if all elements are equal.