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()

PHP手册 - N: Sorting Arrays

用户评论:

oculiz at gmail dot com (12-Mar-2011 05:57)

Another way to do a case case-insensitive sort by key would simply be: <?php uksort($array, 'strcasecmp'); ?> Since strcasecmp is already predefined in php it saves you the trouble to actually write the comparison function yourself.

K.i.n.g.d.r.e.a.d (06-Apr-2010 02:29)

If you search a feature which sorts an array incasesensitive by key, try this: <?php function isort($a,$b) { return strtolower($a)>strtolower($b); } uksort($array, "isort"); ?>

Dirk (29-Mar-2010 09:32)

If you need to perform any of these sort functions on an array containing two or more equivalent values, you can get the equivalents to fall next to each other within the overall ordering (similar to how MySQL's ORDER BY works...) instead of breaking the sort() function, by using ksort() as a second parameter to arbitrarily distinguish any equivalent values by their unique keys: <?php sort($array, ksort($array)); ?> Seems like this effect should be built in. At least the workaround is so short...