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()