Code Help - Signature Checking

[Alexia]

I can't quite figure out what is going wrong with this code. It is supposed to pull the user's signature from the database and check to make sure it isn't empty. However, it isn't even getting the signature to check. This is in the file newthread.php.

PHP Code:

// ~~~~#### SIGNATURE CHECK by ALEXIA####~~~~
$signaturenotnull = $DB_site->query("SELECT signature FROM usertextfield WHERE userid = " . $bbuserinfo[userid]);

echo $signaturenotnull[signature];

if (empty($signaturenotnull[signature]))
{
    eval(print_standard_error('signaturenotset'));
}
// ~~~~#### SIGNATURE CHECK by ALEXIA####~~~~