returns an array containing all of the remaining rows in the result set. The array represents each row as either an array of column values or an object with properties corresponding to each column name. An empty array is returned if there are zero results to fetch, or FALSE on failure.
Using this method to fetch large result sets will result in a heavy demand on system and possibly network resources. Rather than retrieving all of the data and manipulating it in PHP, consider using the database server to manipulate the result sets. For example, use the WHERE and ORDER BY clauses in SQL to restrict results before retrieving and processing them with PHP.