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(PHP 4, PHP 5)
arsort — Sortiert ein Array in umgekehrter Reihenfolge und erhält die Index-Assoziation
Diese Funktion sortiert ein Array so, dass der Zusammenhang zwischen den Indizes und den entsprechenden Elementen des Arrays erhalten bleibt.
Dies wird hauptsächlich zur Sortierung assoziativer Arrays verwendet, bei denen die aktuelle Reihenfolge der Elemente bedeutend ist.
Das Eingabe-Array.
Sie können das Verhalten der Sortierung mittels dem optionalen Parameter sort_flags beeinflussen, für Details siehe sort().
Gibt bei Erfolg TRUE zurück. Im Fehlerfall wird FALSE zurückgegeben.
Beispiel #1 arsort()-Beispiel
<?php
$fruits = array("d" => "Zitrone", "a" => "Orange", "b" => "Banane", "c" => "Apfel");
arsort($fruits);
foreach ($fruits as $key => $val) {
echo "$key = $val\n";
}
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
d = Zitrone a = Orange b = Banane c = Apfel
Die Früchte wurden in umgekehrter alphabetischer Reihenfolge sortiert und die Zuordnung zwischen Index und Element blieb erhalten.
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
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.
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.
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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