There are lots of PHP defined function to order arrays (the core of PHP, technically are hashmaps), ordering by value or keys, preserving key order or not, using an user-defined function, normal or reverse order, etc...
Following, some clear example of the main ones, and some tips about how to remember them
ORDER BY VALUE
sort(): order by VALUE (keys destroyed and renumberted starting from zero)
$a = array('z'=>'A', 'y'=>'C','k'=>'B','x'=>'B');
sort( $a ); # Array ( A ,B ,B ,C )
asort(): as the previous, but it maintains index association
$a = array('z'=>'A', 'y'=>'C','k'=>'B','x'=>'B');
asort( $a ); # Array ( [z] => A , [k] => B , [x] => B , [y] => C )
natsort(): use "natural" sorting
$a = array('z'=>'5p', 'y'=>'10p','20p');
sort( $a ); # Array ( 10p ,20p ,5p )
natsort( $a ); # Array ( [2] => 5p , [0] => 10p , [1] => 20p )
ORDER BY KEY
ksort(): order by key (maintaining associations)
$a = array('z'=>'A', 'y'=>'C','k'=>'B','x'=>'B');
ksort( $a ); # Array ( [k] => B , [x] => B , [y] => C , [z] => A )
USER-DEFINED COMPARISON FUNCTION
usort(): compare using an user-defined function. (keys destroyed and renumbered starting from zero)
$a = array( '0'=>array('id'=>4,'n'=>'aaa') , '1'=>array('id'=>2,'n'=>'bbb')
usort($a, function ($a, $b) { #order by '[id]' contained in the elements #closure (php 5.3)
return ($a['id'] < $b['id']) ? -1 : 1; }); #Array ( Array ( [id] => 1 [n] => ccc ) ,Array ( [id] => 2 [n] => bbb ) ,Array ( [id] => 4 [n] => aaa ) )
uasort(): as usort but MAINTAINS the KEYS
HOW TO REMEMBER FUNCTION NAMES
sort = default sort behaviour: order by value and destroy keys
If the function name contains:
u = sort using [U]ser-defined function (Usort, Uasort, Uksort)
a = [A]ssociative: maintains key order (Asort, Arsort, uAsort)
k = order by [K]ey (Ksort, Krsort)
r = [R]everse order (aRsort, kRsort, Rsort)
OTHER ARRAY USEFUL FUNCTIONS
shuffle(): scramble array s contents. (keys destroyed and renumberted starting from 0)
array_rand($array, $number): return $number random elements from $array
array_multisort()
array_shift( array &$array ) ; return the array shifted by 1element off the beginning of array (remove the 1st)
array_slice( array $array , 3, 2, $preserve_keys); RETURNS 2 elements starting from the 4th. if $preserve_keys is true, the keys in the return array are the same in the original one
$a = array(0=>1, 1=>2, 2=>3, 4=>4, 3=>5, 5=>6);
$a = array_slice($a,3,2); #Array ( 4 ,5 )
array_splice(): remove the slice (REFERENCE) and return the removed part
$a = array(1, 2, 3, 4, 5, 6);
$returned = array_splice($a,3,2); #remove 2 elements from 4th elem. return the removed slice
# $returned = Array ( 4 ,5 )
# $a = Array ( 1 ,2 , 3 , 6 )
