FieldsHelper.php

<?php

use Symfony\Component\HttpFoundation\Request;
/**
 * @see https://github.com/symfony/symfony/pull/18834
 */
class FieldsHelper
{
    private function __construct()
    {
    }

    /**
     * ?fields[]=foo&fields[]=bar.baz.qux&fields[]=baz.qux&fields[]=qux
     * => ['foo', 'bar' => ['baz' => 'qux'], 'baz' => 'qux', 'qux']
     */
    public static function extractFieldsFromRequest(Request $request): array
    {
        $fields = [];

        if (!is_array($queryFields = $request->query->get('fields'))) {
            return $fields;
        }

        foreach ($queryFields as $queryField) {
            $field = static::convertQueryField($queryField);

            if (is_array($field)) {
                $fields = array_merge_recursive($fields, $field);
            } else {
                $fields[] = $field;
            }
        }

        return $fields;
    }

    /**
     * foo.bar.baz.qux
     * => ['foo' => ['bar' => ['baz => 'qux']]]
     *
     * foo
     * => 'foo'
     *
     * foo.bar
     * => ['foo' => 'bar']
     */
    public static function convertQueryField(string $field)
    {
        $explodedField = explode('.', $field, 2);

        if (!isset($explodedField[1])) {
            return $explodedField[0];
        }

        $convertedField[$explodedField[0]] = static::convertQueryField($explodedField[1]);

        return $convertedField;
    }
}