arsort

(PHP 4, PHP 5)

arsort — Ordina un array in ordine decrescente e mantiene le associazioni degli indici

Descrizione

bool arsort ( array $array [, int $sort_flags ] )

Questa funzione ordina un array in modo tale che i suoi indici mantengano la loro correlazione con gli elementi ai quali sono associati. Viene usata principalmente nell'ordinamento degli array associativi, quando la disposizione originaria degli elementi è importante.

Restituisce TRUE in caso di successo, FALSE in caso di fallimento.

Example #1 esempio di arsort()


<?php
$frutta = array("d" => "limone", "a" => "arancia", "b" => "banana", "c" => "mela");
arsort($frutta);
reset($frutta);
while (list($chiave, $valore) = each($frutta)) {
    echo "$chiave = $valore\n";
}
?>

Questo esempio mostrerà:

c = mela
d = limone
b = banana
a = arancia

I frutti sono ordinati in ordine alfabetico decrescente, e l'indice associato a ogni elemento è stato mantenuto.

È possibile modificare il comportamento dell'ordinamento usando il parametro opzionale sort_flags , per maggiori dettagli vedere sort().

vedere anche asort(), rsort(), ksort() e sort().

asort

array

Last updated: Fri, 18 Jul 2008

add a note User Contributed Notes
arsort

jordancdarwin at googlemail dot com
15-Dec-2007 11:21


A lot of people seem to trip up on this and ask me questions as to debugging. Bear in mind that this returns boolean, and does not return an array of affected items. 



$array = array("One"=>1, "Three" => 3,"Two" =>2);

print_r(asort($array));



If successful, will return 1, and error if there is a string used. Useful to note so then people stop asking me :D

Scott Woods
02-Feb-2005 05:21


Note about "morgan at anomalyinc dot com"'s comment:



As of PHP4, you can just use array_multisort() to sort parallel or multi-dimensional arrays.

rodders_plonker at yahoo dot com
22-Aug-2000 03:43


I was having trouble with the arsort() function on an older version of PHP which was returning an error along the lines of 'wrong perameter count for function arsort' when I tried to use a flag for numeric sorting (2/SORT_NUMERIC).


I figured, as I only wanted to sort integers, I could pad numbers from the left to a specific length with 0's (using the lpad function provided by improv@magma.ca in the notes at http://www.php.net/manual/ref.strings.php).


A string sort then correctly sorts numerically (i.e. {30,2,10,21} becomes {030,021,010,002} not {30,21,2,10}) when echoing the number an (int)$string_name hides the leading 0's.





Made my day :).





Rodders.

morgan at anomalyinc dot com
25-Nov-1999 04:30


If you need to sort a multi-demension array, for example, an array such as 





$TeamInfo[$TeamID]["WinRecord"] 


$TeamInfo[$TeamID]["LossRecord"] 


$TeamInfo[$TeamID]["TieRecord"] 


$TeamInfo[$TeamID]["GoalDiff"]


$TeamInfo[$TeamID]["TeamPoints"] 





and you have say, 100 teams here, and want to sort by "TeamPoints":





first, create your multi-dimensional array. Now, create another, single dimension array populated with the scores from the first array, and with indexes of corresponding team_id... ie


$foo[25] = 14


$foo[47] = 42


or whatever.


Now, asort or arsort the second array.


Since the array is now sorted by score or wins/losses or whatever you put in it, the indices are all hoopajooped.


If you just walk through the array, grabbing the index of each entry, (look at the asort example. that for loop does just that) then the index you get will point right back to one of the values of the multi-dimensional array.


Not sure if that's clear, but mail me if it isn't...


-mo

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asort

array

Last updated: Fri, 18 Jul 2008