how to store return value of function in database?

hello everybody

i want to store string value (return from function) in database.this value is special for each user,like password.this is my function:

public function createSecret($secretLength = 16)
        $validChars = $this->_getBase32LookupTable();

        $secret = '';
        for ($i = 0; $i < $secretLength; $i++) {
            $secret .= $validChars[array_rand($validChars)];
        return $secret;

which table is appropriate to store?and how to store?please help me.