MDB : inserting NULL timestamp

Hi, I use MDB to insert a timestamp into a MS SQL table. If the timestamp is non empty, ok if the timestamp value is empty, I would like to insert a NULL rather than a '', because MSSQL encodes the default 01/01/1900 The Common.php reads : function getTimestampValue($value) { return(($value === NULL) ? 'NULL' : "'$value'"); } So, I tried to check if the php value I want to insert is empty or not. If empty, then assign it the php NULL if(trim($value)=='') then value= NULL; But This does not work. The 01/01/1900 is always inserted with empty dates Did I miss something? Note : I use a prepared query inside another class, so i cannot directly use the setParamNull() function to set the NULL value to the prepared query Thank you , Vincent