Description:
------------
In the PEAR DB module, the quoteString function returns the string "NULL" when passed a null.  This makes a literal "NULL" get written into the database which is a problem.  For better backwards compatibility with the pre-quote() API please consider this implementation for pear/DB/common.php:


    function quoteString($string)
    {
        $string = $this->quote($string);
        if ($string == "NULL")
            return "";
        if ($string{0} == "'") {
            return substr($string, 1, -1);
        }
        return $string;
    }


Reproduce code:
---------------
$val=$dbh->getOne("select null");
echo "The value is:", $dbh->quote($val);

Expected result:
----------------
The value is:

Actual result:
--------------
The value is:NULL