PHP: arsort - Manual

Description

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

This function sorts an array such that array indices maintain their correlation with the array elements they are associated with. This is used mainly when sorting associative arrays where the actual element order is significant.

Returns TRUE on success or FALSE on failure.

Example 1. arsort() example


<?php

$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");

arsort($fruits);

reset($fruits);

while (list($key, $val) = each($fruits)) {

    echo "$key = $val\n";

}

?>

The above example will output:

a = orange
d = lemon
b = banana
c = apple

The fruits have been sorted in reverse alphabetical order, and the index associated with each element has been maintained.

You may modify the behavior of the sort using the optional parameter sort_flags, for details see sort().

See also asort(), rsort(), ksort(), and sort().

User Contributed Notes
arsort

Scott Woods
02-Feb-2005 10:21


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
21-Aug-2000 08:43


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
24-Nov-1999 09:30


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