PHP, Put unknown number of column into an array

As stated in a comment, a little database normalization might come in handy. Off the top of my head:

users (id, nick, ...)
rights (id, name, desc, ...)
users_rights (user_id, right_id, issue_date, expiry_date, ...)

Then you could select by JOINing the tables:

SELECT
    ur.user_id,
    r.name
FROM
        rights AS r
    LEFT JOIN
        users_rights AS ur
    ON
        ur.right_id = r.id

(untested)

For a generic insert solution, create a function that takes a hash array, E.g.

$my_array = ('userid' => value1, 'right1' => value 2, etc...);

then pass it into a function like;

function create($values) {
        // get the arguements passed
        $elements = func_get_args();
        // initialise the array for the paramters
        $sql_array = array();
        // initialise the bindings array
        $bindings = '';

        // start the sql
        $sql = "INSERT INTO `{$this->db_table}` (";

        // loop over the parameters
        foreach ($elements[0] as $k => $v) {
            // add to sql statement
            $sql .= "`$k`,";
            // add to bindings string
            $bindings .= "?,";
            // add to sql parameter array
            $sql_array[] = $v;
        }

        // remove the last ' from the sql statement
        $sql = rtrim($sql, ',');
        // now add closing bracket, and start of values
        $sql .= ") VALUES (";
        // remove the last ' from the sql statement
        $bindings = rtrim($bindings, ',');
        // now add bindings to the sql, and close it off
        $sql = $sql . $bindings . ')';

        // run the query in your preferred method, remembering to check for errors
    }

As suggested above, data normalization is your friend here, but if you really have to:

$res = mysql_query ( "SELECT * FROM ..." );
$rights = array();
while ( $r = mysql_fetch_assoc ( $res ) ) {
  $rights[$r['usersid']] = $r;
}

You can now access the users' permissions through $rights[<userid>]['rightsX']