Help with Php Mysql Insert?

[Jeremy F]

I need a bit of help.
Can anyone tell me why this wont work.
$sql="INSERT INTO bl_key (Key, Name, bl_id, whosub)
VALUES
('$_POST[blkey]','$_POST[name]','$_POST[blid]','$_POST[whosub]')";

if (!mysql_query($sql,$dbcnx))
{
die('Error: ' . mysql_error());
}
echo "1 record added";

Above is Insert.php

<form action="insert.php" method="post">
Who is submitting: <input type=text name=whosub><br>
Name on BL ID: <input type=text name=name><br>
De-activated Blockland Key.<input type=text name=blkey> <small><small><i>*Note: Please only enter De-activated keys.</i></small></small><br>
BL ID: <input type=text name=blid><br>
<input type="submit" />
</form>

Above is index.php

I'm not sure why this is not working.
Please help