Predefined Constants
Array Functions
Arrays
PHP Manual

# 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()

Predefined Constants
Array Functions
Arrays
PHP Manual