How about
$sql = mysql_query("SELECT yourcolumn FROM yourtable WHERE condition",$db);
while ($myrow = mysql_fetch_array($sql)) {
$your_array[] = $myrow["yourcolumn"];
}
Something like this should do the job, just play around with it a bit.
It assumes that you already have a database connection $db and that you have already selected the database to use and that you are using MySQL.
Hope this helps
Paul