MySQL Var column

[Derick88]

Hello,
I need help with this script. Look at the line 10, I wrote ....SET $bbid.... It's a variable, I think it's not working fine. Is there a better way??
Thanks!

$a = time();
$b1=mysql_query("SELECT * FROM batisse WHERE finish < '$a'");
while($r=mysql_fetch_assoc($b1)){
$a = time();
$bid = $r['id'];
$buser = $r['u'];
$bbid = $r['bid'];
$bcid = $r['bcid'];
$lv = $r['lv'];
mysql_query("UPDATE `continent` SET `$bbid` = '$lv' WHERE `bcid` = '$bcid'");
mysql_query("DELETE FROM `batisse` WHERE `id` = '$bid'");
}