Php equal functions return different values

I have this function:

function login($username, $password) {
    $user_id = user_id_from_user_name($username);

    $username = sanitize($username);
    $password = md5($password);

    return (mysql_result(mysql_query("SELECT COUNT('user_id')  FROM 'users' WHERE
        'username' = '$username' AND 'password' = '$password'"), 0) == 1) ? $user_id : false;
}

Which is the one that returns the correct result ( true if the username and pass match) but this one down, that I do not see diff no difference no longer works. Does anyone know what I'm doing wrong?

function login($username, $password) {
    $user_id = user_id_from_user_name($username);
    $query = mysql_query("SELECT COUNT('user_id')  FROM 'users' WHERE 'username' = '$username' AND 'password' = '$password'");

    $username = sanitize($username);
    $password = md5($password);

    return (mysql_result($query, 0) == 1) ? $user_id : false;
}