include php file then make a call_user_func() doesn't work

Question

I have got a little problem. My script gets module names to include by database. In these files their is just one function (same name as the file name). My though was that this code should work:

But unfortunately it doesn't work. If I call the function directly it works.

if(mysqli_num_rows($result) > 0)
{
    while($row = mysqli_fetch_array($result))
    {
        if(get_user_right('dashboard_'.$row['name']))
        {
            if(file_exists('module/'.$row['name'].'.php'))
            {
                include('module/'.$row['name'].'.php');
                $content .= call_user_func($row['name']);
            }
        }
    }
}