From the link:

function news_read($limit = 0) {
	if($limit == 0)
		$qry = "SELECT * FROM news ORDER BY n_id DESC";
	else
		$qry = "SELECT * FROM news ORDER BY n_id DESC LIMIT $limit";
	echo $qry;
	$stmt = $this->db->prepare($qry);
	$stmt->execute();
	$stmt->bind_result($n_id,$n_title,$n_note,$n_time,$n_author);
	while($stmt->fetch()) {
		$n_ids[] = $n_id;
		$n_titles[] = $n_title;
		$n_notes[] = $n_note;
		$n_times[] = $n_time;
		$n_authors[] = $n_author;
		$stmnt->free_result;
	}
	$stmt->close();
	return array(ids => $n_ids, titles => $n_titles, notes => $n_notes, times => $n_times, authors => $n_authors);
}

This is a known limitation of ext/mysqli when using libmysql (always in 5.2 and previous) and when libmysql is enabled with 5.3 . The reason is that the server sends not too specific metadata about the column. This longtext has a max length of 4G and ext/mysqli tries to bind with the max length, to be sure no data loss occurs (data doesn't fit in the bind buffer on C level). However, that means 4G for a longtext/longblob column. ext/mysqli has been changed to have a way to work around that. You need to call mysqli_stmt_store_result() which will store the data locally, which means, of course a higher memory usage for PHP. However, because you use libmysql this won't hit the PHP's memory limit, for sure. During store_result the max_length of every column will be calculated and then when bind_result is executed only a buffer with size of max_length will be allocated, which will be definitely lower than 4G.
In short,
prepare
execute
store_result
bind_result
fetch...fetch...fetch

Best,
Andrey