This function implements a sort algorithm that orders alphanumeric strings in the way a human being would. This is described as a "natural ordering".
natcasesort() is a case insensitive version of natsort(). See natsort() for an example of the difference between this algorithm and the regular computer string sorting algorithms.
For more infomation see: Martin Pool's Natural Order String Comparison page.
See also sort(), natsort(), strnatcmp(), and strnatcasecmp().