rsort

(PHP 4, PHP 5)

rsort — Sort an array in reverse order

Description

bool rsort ( array &$array [, int $sort_flags ] )

This function sorts an array in reverse order (highest to lowest).

Parameters

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

Return Values

Returns TRUE on success or FALSE on failure.

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.

Notes

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.


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

   }

?>

pshirkey at boosthardware dot com
14-Jan-2005 09:06


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");

ray at non-aol dot com
02-Nov-2004 03:49


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.

rnk-php at kleckner dot net
17-Jun-2003 07:37


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.

slevy1 at pipeline dot com
13-Jun-2001 06:15


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.

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Last updated: Fri, 02 Jan 2009