Problemi con insert

[camionistaxcaso]

Qualcuno che mi sa dire perchè non mi fa questa insert?

if($_POST["status"] == "Chiusa")    
{        $closed_date = ", CURRENT_DATE()";    }
   
else{ $closed_date = ", ''";}
$sql = "INSERT INTO t_staff_notes                     
             (id_staff, note, status, date, last_date, closed_date)                     
             VALUES ('".$_SESSION["id_username"]."',                    
             '".$_POST["note"]."',                    
             '".$_POST["status"]."',                     
             CURRENT_DATE(),                    
             CURRENT_DATE() ".$closed_date;

//se c' è un errore    
if(!mysql_query($sql))           
{                       
        //Stampo messaggio avvisando dell' errore nella query       
       header("location: home_notes.php?sez=note_form&msgerror=2");            
}    

else    {        

                //Stampo messaggio di buon fine      
               header("location: home_notes.php?msginfo=1");
             } 

La query stampata a video con php:

INSERT INTO t_staff_notes (id_staff, note, status, date, last_date, closed_date) VALUES ('77', 'valore', 'Chiusa', CURRENT_DATE(), CURRENT_DATE() , CURRENT_DATE()

Mi da queta notice:

Notice: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 7 in C:\Program Files\xampp\htdocs\bs_site\home\staff\notes\insert _or_update.php on line 108


​Grazie