Fetch all values from sqlite DB with PHP

Although I am quite familiar with PHP, I am a newbie in sqlite. I am trying to fetch all values from a Data Table, but I can't get my code to work. After a little research I got this code, but it just doesn't work:

<?php
    echo "1";
    $dir = "sqlite:/data/Adrian/zusatzstoffe.db";
    $dbh = new PDO($dir) or die ("cannot open database");

    echo "2";

    $stmt = $dbh->prepare("SELECT * FROM zusatzstoffe");
    echo "2.5";
    $stmt->execute();
    $arr = $stmt->fetchArray();

    echo "3";

    $arr_count = count($arr);
    echo $arr_count;
    echo "4,";

    echo $arr;

My code is running until "2.5". I am using this simple way to find my error, since the server I am using, doesn't show an error log.