echo with insert doesn't work

hi i'm trying to add some values into sqlite db, ido a php function like that:

function addConvexArea($convexArea , $db, $roomId){

$idIndexArray = array();


for ($i=0;$i < sizeof($convexArea);$i++)
{

$sql = "INSERT INTO ConvexArea (ID_room)
        VALUES (".$roomId.") ";

$insert = $db->query($sql);

echo 'foo';


}

return $idIndexArray;

}

and put the statements into file insertConvexArea.php. i call that function into another file php after i've include it with include 'insertConvexArea.php'; commands.

now the problem is that the value are correctly inserted but echo don't work why?