Using PHP's array_filter() to Filter Arrays

In PHP programming, arrays are a fundamental data type, and filtering array elements is a common operation. PHP offers the useful array_filter() function to accomplish this task.

The array_filter() function applies a callback to each element of an array, keeping only those elements that satisfy the callback's condition and returning a new array.

Usage syntax:

array array_filter ( array $array [, callable $callback [, int $flag = 0 ]] )

Parameter description:

$array : the array to be filtered.

$callback : a user‑defined function that receives an array element and returns true to keep the element or false to discard it. If omitted, the function removes elements that are falsy.

$flag (optional): determines how many arguments are passed to the callback. The default 0 passes only the value; a value greater than 0 also passes the key as a second argument.

Example 1 – Filtering even numbers:

<?php
// Original array
$arr = [1, 2, 3, 4, 5, 6];

// Callback function
function filter_even($value) {
    return ($value % 2 == 0);
}

// Apply array_filter()
$new_arr = array_filter($arr, 'filter_even');

// Output result
print_r($new_arr);
?>

Running the code outputs:

Array
(
    [1] => 2
    [3] => 4
    [5] => 6
)

Example 2 – Removing empty values from an associative array:

<?php
// Original array
$arr = ['name' => 'Tom', 'age' => '', 'gender' => 'male', 'email' => ''];

// Callback function
function filter_empty($value) {
    return ($value !== '');
}

// Apply array_filter()
$new_arr = array_filter($arr, 'filter_empty');

// Output result
print_r($new_arr);
?>

Running the code outputs:

Array
(
    [name] => Tom
    [gender] => male
)

These examples show two typical scenarios for using array_filter() . In real‑world development, the function has many other applications, and developers can adapt it to various filtering needs.

In summary, array_filter() is a widely used and practical PHP function that provides a convenient way to filter array elements using custom logic, enabling flexible data processing in backend applications.