Build tree using SQLite and php - error with fetchArray

I use SQLite and PHP. I need build some tree like this

• rootfolder - orange_folder1 - orange1


• rootfolder - orange_folder2 - orange2


• rootfolder - banana1 - freshbanana - banana1


• rootfolder - banana1 - freshbanana - banana2


• rootfolder - banana1 - notfreshbanana - banana1


• rootfolder - banana2 - notfreshbanana - banana1


• rootfolder - banana2 - notfreshbanana - banana2


• etc.

But I get error with fetchArray

or

I get tree like this: - rootfolder - orange_folder1 - orange1 - rootfolder - orange_folder2 - orange2 - rootfolder - banana1 - freshbanana - banana1 - rootfolder - banana1 - freshbanana - banana2 - rootfolder - banana1 - notfreshbanana - banana1 - rootfolder - banana2 - notfreshbanana - banana1 - rootfolder - banana2 - notfreshbanana - banana2 - orange1 - orange2 - banana1 - banana2 - banana1 - banana1 - banana2

I created DB in SQLite

<?php
$db = new SQLite3("name.sqlite");

$db->exec('CREATE TABLE food (id INTEGER PRIMARY KEY, parent_folder_id INTEGER, name VARCHAR(10), type VARCHAR(10);');

$db->exec('INSERT INTO food (id, parent_folder_id, name, type) VALUES (1,null,"orange_folder1","folder");'); //in root
$db->exec('INSERT INTO food (id, parent_folder_id, name, type) VALUES (2,1,"orange1","file");'); // in orange folder
?>

Then I use this code:

<?php
    function handler($directory){   

        global $db;
        $stmt = $db->prepare('SELECT * FROM food'. ( $directory=='/' ? '' : (  ' WHERE parent_folder_id=' . $directory ) ) .';');
        $result = $stmt->execute();

        $data = array();

        while ($row = $result->fetchArray()){
            $temp_data = array(
                "id" => $row['id'],
                "name" => $row['name'],
                "type" => $row['type']
            );

            if ($row['type']=='folder'){
                /*$temp_arr = array();
                $stmt = $db->prepare('SELECT * FROM food WHERE parent_id=' . $temp_data["id"].";");
                $result1 = $stmt->execute();
                while ($row1 = $result1->fetchArray()){ 
                    array_push($temp_arr, array(
                                                "id"=> $row1['id'], 
                                                "name"=> $row1['name'], 
                                                "type"=> $row1['type']
                                                )
                            );                  
                }
                $temp_data["data"] = $temp_arr;*/
                $temp_data["data"] = dir($row["id"]);
            }

            $data[] = $temp_data;
        }

        $db->close();

        return $data;
    }

    handler('/');
?>

Thanks.