re-creating a variable name

Hello, I'm having difficulty dynamically creating a variable name for mysql_query. I've tried using variable variables. I tried to re-create the sql string by $a = "update table set startdate='$startdate" $a .= $i ." ' where id=$i"); but that didn't work. I'm dynamically creating each name of the input tag. My input tag is: name=startdate<?echo id ?> but when I use $query = mysql_query("select * from table"); $num_rows = mysql_num_rows($query); for($i=1;$i<=$num_rows;$i++){ $updatesql = mysql_query("update table set startdate='$startdate.=$i' where id=$i"); } It doesn't execute. Can someone tell me what I'm doing wrong. Any help would be greatly appreciated. Thanks Cory