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rsort

(PHP 4, PHP 5, PHP 7, PHP 8)

rsortSort an array in descending order

Description

rsort(array &$array, int $flags = SORT_REGULAR): true

Sorts array in place by values in descending order.

Note:

If two members compare as equal, they retain their original order. Prior to PHP 8.0.0, their relative order in the sorted array was undefined.

Note: This function assigns new keys to the elements in array. It will remove any existing keys that may have been assigned, rather than just reordering the keys.

Note:

Resets array's internal pointer to the first element.

Parameters

array

The input array.

flags

The optional second parameter flags may be used to modify the sorting behavior using these values:

Sorting type flags:

Return Values

Always returns true.

Changelog

Version Description
8.2.0 The return type is true now; previously, it was bool.

Examples

Example #1 rsort() example

<?php
$fruits
= array("lemon", "orange", "banana", "apple");
rsort($fruits);
foreach (
$fruits as $key => $val) {
echo
"$key = $val\n";
}
?>

The above example will output:

0 = orange
1 = lemon
2 = banana
3 = apple

The fruits have been sorted in reverse alphabetical order.

See Also

add a note

User Contributed Notes 6 notes

up
4
Alex M
19 years ago
A cleaner (I think) way to sort a list of files into reversed order based on their modification date.

<?php
$path
= $_SERVER[DOCUMENT_ROOT]."/files/";
$dh = @opendir($path);

while (
false !== ($file=readdir($dh)))
{
if (
substr($file,0,1)!=".")
$files[]=array(filemtime($path.$file),$file); #2-D array
}
closedir($dh);

if (
$files)
{
rsort($files); #sorts by filemtime

#done! Show the files sorted by modification date
foreach ($files as $file)
echo
"$file[0] $file[1]<br>\n"; #file[0]=Unix timestamp; file[1]=filename
}
?>
up
1
ray at non-aol dot com
19 years ago
Like sort(), rsort() assigns new keys for the elements in array. It will remove any existing keys you may have assigned, rather than just reordering the keys. This means that it will destroy associative keys.

$animals = array("dog"=>"large", "cat"=>"medium", "mouse"=>"small");
print_r($animals);
//Array ( [dog] => large [cat] => medium [mouse] => small )

rsort($animals);
print_r($animals);
//Array ( [0] => small [1] => medium [2] => large )

Use KSORT() or KRSORT() to preserve associative keys.
up
-5
slevy1 at pipeline dot com
23 years ago
I thought rsort was working successfully or on a multi-dimensional array of strings that had first been sorted with usort(). But, I noticed today that the array was only partially in descending order. I tried array_reverse on it and that seems to have solved things.
up
-8
pshirkey at boosthardware dot com
19 years ago
I needed a function that would sort a list of files into reversed order based on their modification date.

Here's what I came up with:

function display_content($dir,$ext){

$f = array();
if (is_dir($dir)) {
if ($dh = opendir($dir)) {
while (($folder = readdir($dh)) !== false) {
if (preg_match("/\s*$ext$/", $folder)) {
$fullpath = "$dir/$folder";
$mtime = filemtime ($fullpath);

$ff = array($mtime => $fullpath);
$f = array_merge($f, $ff);

}
}



rsort($f, SORT_NUMERIC);

while (list($key, $val) = each($f)) {
$fcontents = file($val, "r");
while (list($key, $val) = each($fcontents))
echo "$val\n";
}

}
}

closedir($dh);
}

Call it like so:

display_content("folder","extension");
up
-10
rnk-php at kleckner dot net
21 years ago
Apparently rsort does not put arrays with one value back to zero. If you have an array like: $tmp = array(9 => 'asdf') and then rsort it, $tmp[0] is empty and $tmp[9] stays as is.
up
-13
suniafkhami at gmail dot com
10 years ago
If you are sorting an array from a database result set, such as MySQL for example, another approach could be to have your database sort the result set by using ORDER BY DESC, which would be the equivalent of using rsort() on the resulting array in PHP.

[Edited by moderator for clarity: googleguy at php dot net]
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