diff --git a/src/Util/Form/ArrayTransformer.php b/src/Util/Form/ArrayTransformer.php
new file mode 100644
index 0000000000..48c23c7499
--- /dev/null
+++ b/src/Util/Form/ArrayTransformer.php
@@ -0,0 +1,70 @@
+<?php
+
+// {{{ License
+// This file is part of GNU social - https://www.gnu.org/software/social
+//
+// GNU social is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// GNU social is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with GNU social.  If not, see <http://www.gnu.org/licenses/>.
+// }}}
+
+/**
+ * Handle network public feed
+ *
+ * @package  GNUsocial
+ * @category Controller
+ *
+ * @author    Hugo Sales <hugo@fc.up.pt>
+ * @copyright 2020 Free Software Foundation, Inc http://www.fsf.org
+ * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
+ */
+
+namespace App\Util\Form;
+
+use App\Util\Formatting;
+use Symfony\Component\Form\DataTransformerInterface;
+use Symfony\Component\Form\Exception\TransformationFailedException;
+
+class ArrayTransformer implements DataTransformerInterface
+{
+    /**
+     * Array to string, but can't use type annotations
+     *
+     * @param mixed $a
+     */
+    public function transform($a)
+    {
+        if (!is_array($a)) {
+            throw new TransformationFailedException();
+        }
+        return Formatting::toString($a, Formatting::SPLIT_BY_SPACE);
+    }
+
+    /**
+     * String to array, but can't use type annotations
+     *
+     * @param mixed $s
+     */
+    public function reverseTransform($s)
+    {
+        if (empty($s)) {
+            return [];
+        }
+
+        $arr;
+        if (is_string($s) && Formatting::toArray($s, $arr, Formatting::SPLIT_BY_BOTH)) {
+            return $arr;
+        } else {
+            throw new TransformationFailedException();
+        }
+    }
+}