ArrayFilter.php

<?php
namespace Neon1024\ArrayReduce;

class ArrayReduce
{
    /**
     * Reduce an input array by removing fields which are present in the second array argument
     * 
     * @param  array  $target   The array of data to reduce
     * @param  array  $reduceBy Array of array keys to be removed from the target array
     * @return array
     */
    public function reduce(array $target, array $reduceBy)
    {
        $filtered = array_filter($target, function ($value, $key) use ($reduceBy) {
            if (!in_array($key, $reduceBy)) {
                return false;
            }

            return true;
        }, ARRAY_FILTER_USE_BOTH);

        return $filtered;
    }
}

ArrayFilterTest.php

<?php
namespace Neon1024\Tests;

use PHPUnit\Framework\TestCase;
use Neon1024\ArrayReduce\ArrayReduce;

class ArrayReduceTest extends TestCase
{
    public function setUp()
    {
        require 'vendor/autoload.php';
    }

    public function testReduce()
    {
        $fieldToUpdate = [
            'id',
            'name',
            'modified'
        ];

        $responseData = [
            'id' => 9,
            'name' => 'Example',
            'description' => 'The description',
            'something' => 'else',
            'created' => (new \DateTime())->format('Y-m-d\TH:i:sP'),
            'modified' => (new \DateTime())->format('Y-m-d\TH:i:sP')
        ];

        $reducer = new ArrayReduce();
        $result = $reducer->reduce($responseData, $fieldToUpdate);

        $expected = [
            'id' => 9,
            'name' => 'Example',
            'modified' => (new \DateTime())->format('Y-m-d\TH:i:sP')
        ];

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