function find_author_by_id($id)
{
    $sql = "SELECT * " . "FROM authors " . "WHERE id=:id";
    return find_object_by_sql($sql, array(':id' => $id));
}
function find_book_by_id($id)
{
    $sql = "SELECT " . "b.id as id, b.title as title, b.year as year, b.author_id as author_id, " . "a.name as author_name, a.birthday as author_birthdady, a.bio as author_bio " . "FROM books b " . "LEFT JOIN authors a ON a.id=b.author_id " . "WHERE b.id=:id";
    return find_object_by_sql($sql, array(':id' => $id));
}