asort

(PHP 4, PHP 5, PHP 7)

asort — 对数组进行排序并保持索引关系

说明

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

本函数对数组进行排序，数组的索引保持和单元的关联。主要用于对那些单元顺序很重要的结合数组进行排序。

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

可以用可选的参数 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 asort() 例子

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

以上例程会输出：

c = apple
b = banana
d = lemon
a = orange

fruits 被按照字母顺序排序，并且单元的索引关系不变。

参见

User Contributed Notes

aditycse at gmail dot com 07-Aug-2015 09:41
/*
 * Name : Aditya Mehrotra
 * Email: aditycse@gmail.com
 */
//Example for sorting by values for an alphanumeric array also having case-sensitive data
$exampleArray1 = $exampleArray2 = array(
    0 => 'example1',
    1 => 'Example10',
    2 => 'example12',
    3 => 'Example2',
    4 => 'example3',
    5 => 'EXAMPLE10',
    6 => 'example10'
);

//default sorting
asort($exampleArray1);

// alphanumeric with case-sensitive data sorting by values
asort($exampleArray2, SORT_STRING | SORT_FLAG_CASE | SORT_NATURAL);

//output of defaut sorting
print_r($exampleArray1);
/*
 * output of default sorting
  Array
  (
  [5] => EXAMPLE10
  [1] => Example10
  [3] => Example2
  [0] => example1
  [6] => example10
  [2] => example12
  [4] => example3
  )
 */

print_r($exampleArray2);
/*
 * output of alphanumeric with case-sensitive data sorting by values
 Array
(
    [0] => example1
    [3] => Example2
    [4] => example3
    [5] => EXAMPLE10
    [1] => Example10
    [6] => example10
    [2] => example12
)
 */
stephen [ at ] brooksie-net [ dot ] co [ dot ] uk 02-Mar-2013 01:37
It is obviously necessary to log the keys used as so we don't overwrite previous entries in the array ;o)

N.B. this also effects the timings, but still faster than the alternatives :

     * int : 0.00159    (ms)
     * str : 0.00092    (ms)

<?php
private function _keySort(Array $data)
    {
        $keys = array();
       
        foreach($data as $row) {
           
            $keyIncrement =
                (!isset($keys[$row[$this->_orderField]]))
                    ? $keys[$row[$this->_orderField]] = 0
                    : ++$keys[$row[$this->_orderField]];

            $tempArray[$row[$this->_orderField].$keyIncrement] = $row;
        }

        if ($this->_orderDirection == 'DESC') {
            krsort($tempArray, SORT_NATURAL | SORT_FLAG_CASE );
        } else {
            ksort($tempArray, SORT_NATURAL | SORT_FLAG_CASE);
        }

        return $tempArray;          
           
    }
?>
nick ([AT]) nickyost ([DOT]) com 16-Sep-2011 12:32
This function can be used to sort multidimensional arrays with almost no work whatsoever by using the individual values within the custom sort function.

This function passes the entire child element even if it is not a string. If it is an array, as would be the case in multidimensional arrays, it will pass the whole child array as one parameter.

Therefore, do something elegant like this:

<?php
     // Sort the multidimensional array
     usort($results, "custom_sort");
     // Define the custom sort function
     function custom_sort($a,$b) {
          return $a['some_sub_var']>$b['some_sub_var'];
     }
?>

This does in 4 lines what other functions took 40 to 50 lines to do. This does not require you to create temporary arrays or anything. This is, for me, a highly preferred solution.

Hope it helps!
Anon 07-May-2011 02:37
Case insensitive sort in one line:

<?php

array_multisort(array_map('strtolower', $array), $array);

?>
rick at toewsweb dot net 29-Apr-2011 01:40
On sorting by value first, then by key (cf., 2008-01-31 notes by mike at clear-link dot com):

What occurred to me to solve this problem was to extract the keys and values into separate arrays, then use array_multisort to get the desired order:

Ex:
<?php
$kvpairs = array('noun' => 'thought', 'animal' => 'fish', 'abstract' => 'thought', 'food' => 'fish', 'verb' => 'fish');
print "before:\n";
print_r($kvpairs);

// Essentially, one line of code is all that's needed for the sort:
array_multisort(array_values($kvpairs), array_keys($kvpairs), $kvpairs);

print "after:\n";
print_r($kvpairs);
?>

before:
Array
(
    [noun] => thought
    [animal] => fish
    [abstract] => thought
    [food] => fish
    [verb] => fish
)
after:
Array
(
    [animal] => fish
    [food] => fish
    [verb] => fish
    [abstract] => thought
    [noun] => thought
)

Of course, array_multisort allows you to specify sort order (SORT_ASC, SORT_DESC) and sort type (SORT_REGULAR, SORT_STRING, SORT_NUMERIC) for each array you pass it.
Eran 22-Apr-2009 02:15
i made this sample multi dimensional array sort to someone who needed to read lines from a text file instead of using sql - order by statement.

the idea is to take the key and sort(order) the specific column and then order the entire of the array as the selected column asort returned.

<?php
/**
 *
 * This sample is reading text data
 * and perform a sort to a 2 dimensional array
 * just like a normal sql do to "order by asc"
 *
 */

$foo = array();

/*
# SORT_REGULAR - compare items normally (don't change types)
# SORT_NUMERIC - compare items numerically
# SORT_STRING - compare items as strings
*/
$sort_by = SORT_REGULAR;

/*
# 0 - order by name column
# 1 - order by age column
# 2 - order by rank column
# 3 - order by color column
*/
$order_by = 1;

// source file
$line_of_text[1] = 'a1name|f2age|h3rank|jcolor';
$line_of_text[2] = 'b1name|d2age|i3rank|k4color';
$line_of_text[0] = 'c1name|e2age|g3rank|l4color';

// make array
for ($x=0; $x<=2; $x++)
{
    $line = explode('|',$line_of_text[$x]);

    // save it by coulmns otherwise it will saved like rows
    for ($i=0; $i<=3; $i++) {
          $foo[$i][$x] = $line[$i];
    }
}

// get the key order
$a = $foo[$order_by];

// sort
asort($a, $sort_by);

// start print
echo "<table cellpudding=0 cellspacing=0 border=1>\n";
        echo "<tr>\n";
          echo "<td>key</td>\n";
          echo "<td>name</td>\n";
          echo "<td>age</td>\n";
          echo "<td>rank</td>\n";
          echo "<td>color</td>\n";
        echo "</tr>\n";

// print by key order
foreach ($a as $k => $v) {
    echo "<tr>\n";
      echo "<td>$k</td>\n";
      // you can print here a for loop (0 to num of columns[=3])
      echo "<td>".$foo[0][$k]."</td>\n";
      echo "<td>".$foo[1][$k]."</td>\n";
      echo "<td>".$foo[2][$k]."</td>\n";
      echo "<td>".$foo[3][$k]."</td>\n";
    echo "</tr>\n";
}
echo "</table>\n";
?>
bakatamas at freemail dot hu 15-Feb-2008 11:34
Dear mike at clear-link dot com!

I needed a case insensitive version of your function. It is still not perfect as I have to do something with country specific characters (?üó?úéá?í?üó?úéá?í)

function akisort(&$array,$valrev=false,$keyrev=false)
    {
    if ($valrev)
        {
        arsort($array);
        }
        else
        {
        asort($array);
        };
    $vals = array_count_values($array);
    $i = 0;
    foreach ($vals AS $val=>$num)
        {
        $first = array_splice($array,0,$i);
        $tmp = array_splice($array,0,$num);
        $tmp2 = array();
        foreach($tmp as $key => $value)
            {
            $tmp2[] = $key;
            $number = $value;
            };
        natcasesort($tmp2);
        reset($tmp2);
        print_r($tmp2);
        unset($tmp);
        foreach($tmp2 as $key => $value)
            {
            $tmp[$value] = $number;
            };
        if($keyrev)
            {
            $tmp = array_reverse($tmp, true);
            };
        $array = array_merge($first,$tmp,$array);
        unset($tmp);
        $i = $i+$num;
        };
};
mike at clear-link dot com 01-Feb-2008 12:56
Small typo in the aksort function I just submitted. Here's the entire thing again, with the correction noted:

<?php
function aksort(&$array,$valrev=false,$keyrev=false) {
  if ($valrev) { arsort($array); } else { asort($array); }
  $vals = array_count_values($array);
    $i = 0;
    foreach ($vals AS $val=>$num) {
        $first = array_splice($array,0,$i);
        $tmp = array_splice($array,0,$num);
        if ($keyrev) { krsort($tmp); } else { ksort($tmp); }
        $array = array_merge($first,$tmp,$array);
        unset($tmp);
        $i = $i+$num;
        // Fixed from previous post: $i = $num;
    }
}
?>
mike at clear-link dot com 01-Feb-2008 12:23
For a recent project I needed to sort an associative array by value first, and then by key if a particular value appeared multiple times. I wrote this function to accomplish the task. Note that the parameters default to sort ascending on both keys and values, but allow granular control over each.

<?php
function aksort(&$array,$valrev=false,$keyrev=false) {
  if ($valrev) { arsort($array); } else { asort($array); }
    $vals = array_count_values($array);
    $i = 0;
    foreach ($vals AS $val=>$num) {
        $first = array_splice($array,0,$i);
        $tmp = array_splice($array,0,$num);
        if ($keyrev) { krsort($tmp); } else { ksort($tmp); }
        $array = array_merge($first,$tmp,$array);
        unset($tmp);
        $i = $num;
    }
}

// Example
$tmp = array('ca'=>1,'cb'=>2,'ce'=>1,'pa'=>2,'pe'=>1);

// Standard asort
asort($tmp);
print_r($tmp);

// Sort value ASC, key ASC
aksort($tmp);
print_r($tmp);

// Sort value DESC, key ASC
aksort($tmp,true);
print_r($tmp);

// Sort value DESC, key DESC
aksort($tmp,true,true);
print_r($tmp);

// Results
Array
(
    [pe] => 1
    [ca] => 1
    [ce] => 1
    [cb] => 2
    [pa] => 2
)
Array
(
    [ca] => 1
    [ce] => 1
    [pe] => 1
    [cb] => 2
    [pa] => 2
)
Array
(
    [cb] => 2
    [pa] => 2
    [ca] => 1
    [ce] => 1
    [pe] => 1
)
Array
(
    [pa] => 2
    [cb] => 2
    [pe] => 1
    [ce] => 1
    [ca] => 1
)
mzvarik at gmail dot com 16-Jan-2008 06:29
I noticed that my function mentioned earlier is very misleading - somebody please delete that note!

This is how you sort:
<?php
setlocale (LC_ALL, 'czech');
$array = array("a", "?", "c");
usort ($array, 'strcoll');
print_r($array);
?>
przemekkus [at] interia [dot] pl 02-Nov-2007 03:34
Function written by a dot brandon at chello dot nl has an error  - wrong variable name. It should be:

if($rev) arsort($named_hash,$flags=0) ;

instead of

if($reverse) arsort($named_hash,$flags=0) ;
a dot brandon at chello dot nl 26-Jun-2007 04:18
I use this for quasi-SQL orderby. Loosely based on smileaf. Any good for you nerds?

<?

function named_records_sort($named_recs, $order_by, $rev=false, $flags=0)
{// Create 1-dimensional named array with just
 // sortfield (in stead of record) values
    $named_hash = array();
     foreach($named_recs as $key=>$fields)
             $named_hash["$key"] = $fields[$order_by];
 
 // Order 1-dimensional array,
 // maintaining key-value relations  
    if($reverse) arsort($named_hash,$flags=0) ;
    else asort($named_hash, $flags=0);
 
 // Create copy of named records array
 // in order of sortarray 
    $sorted_records = array();
    foreach($named_hash as $key=>$val)
           $sorted_records["$key"]= $named_recs[$key];
 
return $sorted_records;} // named_recs_sort()

function show_sorted_records($named_recs, $order_by, $rev=false, $flags=0)
{$sorted_records=named_records_sort($named_recs, $order_by, $rev, $flags);
foreach($sorted_records as $name=>$fields)
  {echo "<b>$name</b>   ";
   foreach($fields as $field=>$val)
          echo "$field = $val "; echo "<br>";}
} // show_sorted_records()

$girl_friends=array();
$girl_friends["Anna"]=
array("born"=>'1989-08-22',"cupsize"=>'B-',"IQ"=>105, "daddy"=>'rich');
$girl_friends["Zoe"]
=array("born"=>'1978-03-11',"cupsize"=>'C#',"IQ"=>130, "daddy"=>'poor');
$girl_friends["Lilly"]
=array("born"=>'1985-06-16',"cupsize"=>'DD',"IQ"=>90, "daddy"=>'nasty');

$order_by="cupsize"; echo "And the winners are: <br>";
show_sorted_records($girl_friends, $order_by, true);

?>
gunnar at taljaren dot se 14-Jun-2007 10:00
for ($i=0;$i<5;$i++)
   $values[] = $i;
asort($values); 

works, but
for ($i=0;$i<5;$i++)
   $values[$i] =$i;
asort($values);
doesn't!
smileaf at smileaf dot org 25-Jan-2007 03:34
Ok I was mistaken, after re-reading the previous post the ".$key" is important. What caused the sorting issue for me wasn't that at all. But rather something else.
doing an: asort($records, $flags); before returning fixes the sorting problems.
The sorting problem I was refearing to causes a character based sorting done on numeric data.
so instead of:
1
2
3
...
10
12
20
It was returned back as
1
10
12
2
20
3
...
basically what I was trying to fix in the first place.
richard at happymango dot me dot uk 23-Nov-2006 12:52
This is a fixed version of the same function I posted below. Now it will handle duplicate entries in the sorted field. EG: If there were two records that had the name Heathrow it would still work.

<?php

function record_sort($records, $field, $reverse=false)
{
    $hash = array();
   
    foreach($records as $key => $record)
    {
        $hash[$record[$field].$key] = $record;
    }
   
    ($reverse)? krsort($hash) : ksort($hash);
   
    $records = array();
   
    foreach($hash as $record)
    {
        $records []= $record;
    }
   
    return $records;
}

?>
richard at happymango dot me dot uk 22-Nov-2006 12:35
This is a function to sort an indexed 2D array by a specified sub array key, either ascending or descending.

It is usefull for sorting query results from a database by a particular field after the query has been returned

This function can be quite greedy. It recreates the array as a hash to use ksort() then back again

By default it will sort ascending but if you specify $reverse as true it will return the records sorted descending

<?php

function record_sort($records, $field, $reverse=false)
{
    $hash = array();
   
    foreach($records as $record)
    {
        $hash[$record[$field]] = $record;
    }
   
    ($reverse)? krsort($hash) : ksort($hash);
   
    $records = array();
   
    foreach($hash as $record)
    {
        $records []= $record;
    }
   
    return $records;
}

// Example below

$airports = array
(
    array( "code" => "LHR", "name" => "Heathrow" ),
    array( "code" => "LGW", "name" => "Gatwick" ),
);

printf("Before: <pre>%s</pre>", print_r($airports, true));

$airports = record_sort($airports, "name");

printf("After: <pre>%s</pre>", print_r($airports, true));

?>

Example Outputs:

Before: Array
(
    [0] => Array ( [code] => LHR, [name] => Heathrow )
    [1] => Array ( [code] => LGW, [name] => Gatwick )
)

After: Array
(
    [0] => Array ( [code] => LGW, [name] => Gatwick )
    [1] => Array ( [code] => LHR, [name] => Heathrow )
)
php at web-in-time dot com 05-Sep-2006 11:47
acecream's function works fine, especially with the spectre extension.

nevertheless sometimes the index values have to be kept. To achieve this, just replace:

$sorted_arr[] = $array[$arr_key]; 

with:

$sorted_arr[$arr_key] = $array[$arr_key];
rojaro 24-Jun-2004 04:38
Advanced sort array by second index function, which produces ascending (default) or descending output and uses optionally natural case insensitive sorting (which can be optionally case sensitive as well).
Only the first two arguments are required.

<?php

function sabsi ($array, $index, $order='asc', $natsort=FALSE, $case_sensitive=FALSE) {
  if(is_array($array) && count($array)>0) {
    foreach(array_keys($array) as $key) $temp[$key]=$array[$key][$index];
    if(!$natsort) ($order=='asc')? asort($temp) : arsort($temp);
    else {
      ($case_sensitive)? natsort($temp) : natcasesort($temp);
      if($order!='asc') $temp=array_reverse($temp,TRUE);
    }
    foreach(array_keys($temp) as $key) (is_numeric($key))? $sorted[]=$array[$key] : $sorted[$key]=$array[$key];
    return $sorted;
  }
  return $array;
}

?>
spectre at hellfish dot NOSPAM dot org 28-Apr-2003 06:54
that works nicely, tho it breaks the result-array up if one or more of arrays indexes are deleted before sorting. this one should fix it up:

change:
for ($i = 0; $i < sizeof($array); $i++) {

to:
foreach ($array as $i => $k) {
mbevan at marginsoftware dot com 03-Dec-2002 10:25
Nevermind... use my last note as a quick tip: if you wish to keep the keys, use asort() and arsort() in place of sort() and rsort().
01-Aug-2002 03:48
Similar to above but for an array of arrays instead of an array of objects.

<?php
function aasort($x,$var,$cmp='strcasecmp'){
  if ( is_string($var) ) $var = "'$var'";
  uasort($x,
    create_function('$a,$b',
      'return '.$cmp.'( $a['.$var.'],$b['.$var.']);')
  );
  return $x;
}
?>
phzzzt .a.t. acm .d.o.t. org 01-Aug-2002 03:32
Similar to above but for an array of arrays instead of an array of objects.

<?php
function aasort($x,$var,$cmp='strcasecmp'){
  if ( is_string($var) ) $var = "\'$var\'";
  uasort($x,
    create_function('$a,$b',
      'return '.$cmp.'( $a['.$var.'],$b['.$var.']);')
  );
  return $x;
}
?>
salchicha at cable dot net dot co 03-Apr-2002 10:23
Here's one I whipped up to allow you to sort an array of a specific class by a member or function:

<?php
// Sort a class by one of its members (even lowercase!!!)
function casort($arr, $var) {
   $tarr = array();
   $rarr = array();
   for($i = 0; $i < count($arr); $i++) {
      $element = $arr[$i];
      $tarr[] = strtolower($element->{$var});
   }

   reset($tarr);
   asort($tarr);
   $karr = array_keys($tarr);
   for($i = 0; $i < count($tarr); $i++) {
      $rarr[] = $arr[intval($karr[$i])];
   }

   return $rarr;
}
?>

It works very well. For example, I have a Room class with members title, isActive(), date, etc. I can sort an array by casort($rooms, "title") or casort($rooms, "isActive()") and it'll work.
rcwang at cmu dot edu 03-Mar-2002 02:42
Here's my version of sorting multi-dimensional array by 2nd index.
Feel free to change the code to suit your needs.

<?php
function aSortBySecondIndex($multiArray, $secondIndex) {
    while (list($firstIndex, ) = each($multiArray))
        $indexMap[$firstIndex] = $multiArray[$firstIndex][$secondIndex];
    asort($indexMap);
    while (list($firstIndex, ) = each($indexMap))
        if (is_numeric($firstIndex))
            $sortedArray[] = $multiArray[$firstIndex];
        else $sortedArray[$firstIndex] = $multiArray[$firstIndex];
    return $sortedArray;
}
?>
freeman at generalresources dot com 04-May-2001 01:51
The asortbyindex($sortarray, $index) looks like sort not asort. The key of the $sortarray was changed.
sweetland at whoadammit dot com 15-Aug-2000 09:02
Here's a little routine I whipped up to sort multi-dimensional arrays:
<?php
/**
 ** comesafter ($s1, $s2)
 **
 ** Returns 1 if $s1 comes after $s2 alphabetically, 0 if not.
 **/

function comesafter ($s1, $s2) {
        /**
         ** We don't want to overstep the bounds of one of the strings and segfault,
         ** so let's see which one is shorter.
         **/

        $order = 1;

        if (strlen ($s1) > strlen ($s2)) {
                $temp = $s1;
                $s1 = $s2;
                $s2 = $temp;
                $order = 0;
        }

        for ($index = 0; $index < strlen ($s1); $index++) {
                /**
                 ** $s1 comes after $s2
                 **/

                if ($s1[$index] > $s2[$index]) return ($order);

                /**
                 ** $s1 comes before $s2
                 **/

                if ($s1[$index] < $s2[$index]) return (1 - $order);
        }
 
        /**
         ** Special case in which $s1 is a substring of $s2
         **/

        return ($order);
}

/**
 ** asortbyindex ($sortarray, $index)
 **
 ** Sort a multi-dimensional array by a second-degree index. For instance, the 0th index
 ** of the Ith member of both the group and user arrays is a string identifier. In the
 ** case of a user array this is the username; with the group array it is the group name.
 ** asortby
 **/

function asortbyindex ($sortarray, $index) {
        $lastindex = count ($sortarray) - 1;
        for ($subindex = 0; $subindex < $lastindex; $subindex++) {
                $lastiteration = $lastindex - $subindex;
                for ($iteration = 0; $iteration < $lastiteration;    $iteration++) {
                        $nextchar = 0;
                        if (comesafter ($sortarray[$iteration][$index], $sortarray[$iteration + 1][$index])) {
                                $temp = $sortarray[$iteration];
                                $sortarray[$iteration] = $sortarray[$iteration + 1];
                                $sortarray[$iteration + 1] = $temp;
                        }
                }
        }
        return ($sortarray);
}
?>

It's a bit long with all the comments, but I hope it helps.
bwuhlman at tallships dot ca 03-Aug-2000 12:01
Well, actually, asort has *two* annoying features.

It works perfectly well sorting hashes (or associative arrays, as you might have it), but doggedly refuses to sort regular arrays maintaining index assocation. Kind've makes sense, but the docs don't explicitly say you can't do it.

Urgggh.
jacko at kring dot co dot uk 25-Feb-2000 08:26
asort has one anoying feature, it ignores any default or implicit order in the data.  i.e. if two elements of an array contain "banana" then it is not garanteed that the first will still be the first after the sort.
This makes the Burrows-Wheeler block sort a bit of a pain to impliment, with a trailing string having to be appended to all strings before sorting, and removed after sorting. To maintain the so called "banana" order.