Cant write variable into field in mysql

I try to write a variable into the field in MySQL. But i dont have result.
This is my code. Who can help me?

$current_time = & JFactory::getDate();
$time = $current_time->toMySql();
echo $time; //give correct result
$db =& JFactory::getDBO();
$query = "
UPDATE ".$db->nameQuote('jos_chronoforms_newdata')."
SET ".$db->nameQuote('approvaltime')." = $time 
//it's OK if ----   SET ".$db->nameQuote('approvaltime')." = '123456789'
WHERE ".$db->nameQuote('cf_id')." =$index 
";

$db->setQuery($query);
$db->query();

Hi trancompany,

You've quoted all the names but not the value - it needs to be $db->quote($time)

But actually it's simpler to use the MySQL NOW() function

$db =& JFactory::getDBO();
$query = "
  UPDATE ".$db->nameQuote('jos_chronoforms_newdata')."
    SET ".$db->nameQuote('approvaltime')." = NOW()
    WHERE ".$db->nameQuote('cf_id')." = $index
";

Bob

PS $index is OK as it is an integer, strings like '09-09-2009 09:09' need single quotes.

Thank you so much.😀