NULL Problem

Here's my code (using MSSQL): $conn = new COM ("ADODB.Connection")or die("Cannot start ADO"); $conn->open($connStr); $query = "SELECT * FROM TABLE WHERE id = ".$id; $rs = $conn->execute($query); This code works fine, and I retrieve the values like this: $tmp1 = $rs->fields("column1"); $tmp2 = $rs->fields("column2"); Etc... Here's the problem - I'm trying to get a date column that I know is NULL, but I can't seem to get my code right: $tmp = $rs->fields("followup_on"); if(is_null($tmp)){ $followup = ""; }else{ $followup = $rs->fields("followup_on"); } //this results in: Catchable fatal error: Object of class variant could not be converted to string //When I try to ECHO the $followup results (and I know the database value is NULL) So confused - any advice?