array_filter_recursive

gistfile1.php

<?php
/**
 * @param mixed $input
 * @param null|callable $callback
 * @return array
 */
function array_filter_recursive($input, $callback = null) {
    if (!is_array($input)) {
        return $input;
    }
    if (null === $callback) {
        $callback = function ($v) { return !empty($v);};
    }
    $input = array_map(function($v) use ($callback) { return array_filter_recursive($v, $callback); }, $input);
    return array_filter($input, $callback);
}
class FunctionsTest extends \PHPUnit_Framework_TestCase
{
    public function testArrayFilterRecursive()
    {
        $array = [
            'a'=> 'a',
            'b'=> null,
            'c' => [
                'a' => null,
                'b' => 'b',
            ],
            'd' => [
                'a' => null
            ]
        ];

        $result = array_filter_recursive($array);
        $expected = [
            'a'=> 'a',
            'c' => [
                'b' => 'b',
            ],
        ];

        $this->assertSame($expected, $result);
    }

    public function testArrayFilterRecursiveWithCustomCallback()
    {
        $array = [
            'a'=> 'a',
            'b'=> null,
            'c' => [
                'a' => null,
                'b' => 'b',
            ],
            'd' => [
                'a' => null
            ]
        ];

        $result = array_filter_recursive(
            $array,
            function ($value) {
                if (is_array($value)) {
                    return !empty($value);
                }
                return ($value !== null);
            }
        );

        $expected = [
            'a'=> 'a',
            'c' => [
                'b' => 'b',
            ],
        ];

        $this->assertSame($expected, $result);
    }
}