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rsort

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

rsort对数组降序排序

说明

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

本函数按照降序对数组进行排序。

注意:

如果两个成员完全相同,那么它们在排序数组中的相对顺序是未定义的。

参数

array

输入的数组。

flags

可选的第二个参数 flags 可以用以下值改变排序的行为:

排序类型标记:

  • SORT_REGULAR - 正常比较单元 详细描述参见 比较运算符 章节
  • SORT_NUMERIC - 单元被作为数字来比较
  • SORT_STRING - 单元被作为字符串来比较
  • SORT_LOCALE_STRING - 根据当前的区域(locale)设置来把单元当作字符串比较,可以用 setlocale() 来改变。
  • SORT_NATURAL - 和 natsort() 类似对每个单元以“自然的顺序”对字符串进行排序。
  • SORT_FLAG_CASE - 能够与 SORT_STRINGSORT_NATURAL 合并(OR 位运算),不区分大小写排序字符串。

返回值

成功时返回 true, 或者在失败时返回 false

范例

示例 #1 rsort()

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

以上例程会输出:

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

fruits 被按照字母顺序逆向排序。

注释

注意: 此函数为 array 中的元素赋与新的键名。这将删除原有的键名,而不是仅仅将键名重新排序。

参见

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User Contributed Notes 6 notes

up
5
ray at non-aol dot com
16 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
Alex M
16 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
slevy1 at pipeline dot com
20 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
-4
pshirkey at boosthardware dot com
16 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
-5
rnk-php at kleckner dot net
18 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
-7
suniafkhami at gmail dot com
7 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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