Core PHP Programming, Third Edition

21.1. Sorting

To sort means to put a set of like items into order. The rules of ordering can be simple, such as strings sorted by the order of the alphabet. They could be complex, such as sorting addresses first by country, then by state, then by city. The process of sorting can take several forms but always involves comparing two elements with a set of rules for ordering. The result of the comparison determines whether the two items are in order or out of order, therefore needing to be swapped.

There are three classes of sorts: exchange, insert, and select. In an exchange method, two elements are compared and possibly exchanged. This process continues until the list is in order. In an insert method, the elements are removed and placed in another ...