Retrieves the number of rows from a result set.
mysql_num_rows($resultSet) is used to retrieve the number of rows in $resultSet.
It should only be used on a result set generated from a query that produces an actual set of results, such as SELECT. If you want to get the number of rows affected by an UPDATE, DELETE, or INSERT, you should use mysql_affected_rows instead.
It will return the number of rows in the rowset; or boolean FALSE on failure.
Note that as of PHP 5.5.0, this function has been deprecated.
