PHP 7.2.0 Release Candidate 2 Released

rsort

(PHP 4, PHP 5, PHP 7)

rsort对数组逆向排序

说明

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

本函数对数组进行逆向排序(最高到最低)。

Note:

If two members compare as equal, their relative order in the sorted array is undefined.

参数

array

输入的数组。

sort_flags

可以用可选参数 sort_flags 改变排序的行为,详情见 sort()

返回值

成功时返回 TRUE, 或者在失败时返回 FALSE

范例

Example #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

Note: 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
7
ray at non-aol dot com
12 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
0
Alex M
12 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
pshirkey at boosthardware dot com
12 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
-2
slevy1 at pipeline dot com
16 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
-3
suniafkhami at gmail dot com
3 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]
up
-5
rnk-php at kleckner dot net
14 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.
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