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    rsort

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

    rsort — Sort 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:

    • SORT_REGULAR - compare items normally; the details are described in the comparison operators section
    • SORT_NUMERIC - compare items numerically
    • SORT_STRING - compare items as strings
    • SORT_LOCALE_STRING - compare items as strings, based on the current locale. It uses the locale, which can be changed using setlocale()
    • SORT_NATURAL - compare items as strings using "natural ordering" like natsort()
    • SORT_FLAG_CASE - can be combined (bitwise OR) with SORT_STRING or SORT_NATURAL to sort strings case-insensitively

    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

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    User Contributed Notes 6 notes

    up
    3
    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
    2
    ray at non-aol dot com
    20 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
    -2
    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");
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    -3
    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
    -7
    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
    -9
    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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