I can't really help without the error messages, and it's a while since I have used php, but I don't think you can copy an array like that. You would need some sort of counter.
for example
code:
$i = 0;
while ($row_tag = mysql_fetch_array($query_tags)) {
$tags[$i] = $row_tag;
}
I can't remember if $row_tag is an array or not. But something along those lines.