Using PHP's array_filter() Function to Filter Arrays

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

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

Usage syntax:

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

Parameters: $array: the array to be filtered. $callback: a user‑defined function that receives an element and returns true to keep it or false to discard it; if omitted, elements that are falsey are removed by default. $flag (optional): determines how many arguments the callback receives. The default 0 passes only the value; a value greater than 0 also passes the key as the second argument.

Below are two examples demonstrating the use of array_filter():

Example 1: Filtering Even Numbers

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

// Filtering 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 produces:

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

Example 2: Filtering Empty Values from an Associative Array

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

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

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

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

The output is:

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

These examples show two typical scenarios for using array_filter(). In real projects, the function can be applied to many other filtering needs, offering a concise and powerful way to process arrays.

In summary, array_filter() is a widely used PHP function that enables flexible array element filtering through callbacks, helping developers implement various data‑cleaning and selection tasks efficiently.