Sorting Arrays

PHP has several functions that deal with sorting arrays, and this document exists to help sort it all out.

The main differences are:

Some sort based on the array keys, whereas others by the values: $array['key'] = 'value';
Whether or not the correlation between the keys and values are maintained after the sort, which may mean the keys are reset numerically (0,1,2 ...)
The order of the sort: alphabetical, low to high (ascending), high to low (descending), numerical, natural, random, or user defined
Note: All of these sort functions act directly on the array variable itself, as opposed to returning a new sorted array
If any of these sort functions evaluates two members as equal then the order is undefined (the sorting is not stable).

**Sorting function attributes**
Function name	Sorts by	Maintains key association	Order of sort	Related functions
array_multisort	value	associative yes, numeric no	first array or sort options	array_walk
asort	value	yes	low to high	arsort
arsort	value	yes	high to low	asort
krsort	key	yes	high to low	ksort
ksort	key	yes	low to high	asort
natcasesort	value	yes	natural, case insensitive	natsort
natsort	value	yes	natural	natcasesort
rsort	value	no	high to low	sort
shuffle	value	no	random	array_rand
sort	value	no	low to high	rsort
uasort	value	yes	user defined	uksort
uksort	key	yes	user defined	uasort
usort	value	no	user defined	uasort