uasort

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

uasort使用用户定义的比较函数对数组进行排序并保持索引关联

说明

uasort(array &$array, callable $callback): true

本函数对 array 本身排序并保持索引和单元之间的关联。

主要用于对那些单元顺序很重要的结合数组进行排序。比较函数是用户自定义的。

注意:

如果两个成员完全相同,那么它们将保持原来的顺序。 在 PHP 8.0.0 之前,它们在排序数组中的相对顺序是未定义的。

注意:

重置数组中的内部指针,指向第一个元素。

参数

array

输入的数组。

callback

在第一个参数小于,等于或大于第二个参数时,该比较函数必须相应地返回一个小于,等于或大于 0 的整数。

callback(mixed $a, mixed $b): int
警告

从比较函数中返回非整数值,例如 float,将导致内部强制转换为 callback 返回值为 int。因此,诸如 0.990.1 之类的值都将被转换为整数值 0,将这些值比较的话将会是相等。

返回值

总是返回 true

更新日志

版本 说明
8.2.0 现在返回类型为 true;之前是 bool
8.0.0 如果 callback 接受引用传递参数,该方法将会抛出 E_WARNING

示例

示例 #1 uasort() 的基本示例

<?php
// 比较函数
function cmp($a, $b) {
if (
$a == $b) {
return
0;
}
return (
$a < $b) ? -1 : 1;
}

// 要排序的数组
$array = array('a' => 4, 'b' => 8, 'c' => -1, 'd' => -9, 'e' => 2, 'f' => 5, 'g' => 3, 'h' => -4);
print_r($array);

// 排序并打印排序后的数组
uasort($array, 'cmp');
print_r($array);
?>

以上示例会输出:

Array
(
    [a] => 4
    [b] => 8
    [c] => -1
    [d] => -9
    [e] => 2
    [f] => 5
    [g] => 3
    [h] => -4
)
Array
(
    [d] => -9
    [h] => -4
    [c] => -1
    [e] => 2
    [g] => 3
    [a] => 4
    [f] => 5
    [b] => 8
)

参见

add a note add a note

User Contributed Notes 19 notes

up
139
magikMaker
13 years ago
a quick reminder on the syntax if you want to use uasort in a Class or Object:

<?php

// procedural:
uasort($collection, 'my_sort_function');

// Object Oriented
uasort($collection, array($this, 'mySortMethod'));

// Objet Oriented with static method
uasort($collection, array('self', 'myStaticSortMethod'));

?>
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26
yannick dot battail at gmail dot com
13 years ago
An Example using anonymous function.
Anonymous functions make some time the code easier to understand.
<?php
$fruits
= array('Orange9','Orange11','Orange10','Orange6','Orange15');
uasort ( $fruits , function ($a, $b) {
            return
strnatcmp($a,$b); // or other function/code
       
}
    );
print_r($fruits);
?>
returns
Array
(
    [3] => Orange6
    [0] => Orange9
    [2] => Orange10
    [1] => Orange11
    [4] => Orange15
)
up
35
php at clement dot hk
10 years ago
If you want to keep the order when two members compare as equal, use this.
<?php

function stable_uasort(&$array, $cmp_function) {
    if(
count($array) < 2) {
        return;
    }
   
$halfway = count($array) / 2;
   
$array1 = array_slice($array, 0, $halfway, TRUE);
   
$array2 = array_slice($array, $halfway, NULL, TRUE);

   
stable_uasort($array1, $cmp_function);
   
stable_uasort($array2, $cmp_function);
    if(
call_user_func($cmp_function, end($array1), reset($array2)) < 1) {
       
$array = $array1 + $array2;
        return;
    }
   
$array = array();
   
reset($array1);
   
reset($array2);
    while(
current($array1) && current($array2)) {
        if(
call_user_func($cmp_function, current($array1), current($array2)) < 1) {
           
$array[key($array1)] = current($array1);
           
next($array1);
        } else {
           
$array[key($array2)] = current($array2);
           
next($array2);
        }
    }
    while(
current($array1)) {
       
$array[key($array1)] = current($array1);
       
next($array1);
    }
    while(
current($array2)) {
       
$array[key($array2)] = current($array2);
       
next($array2);
    }
    return;
}

function
cmp($a, $b) {
    if(
$a['n'] == $b['n']) {
        return
0;
    }
    return (
$a['n'] > $b['n']) ? -1 : 1;
}

$a = $b = array(
   
'a' => array("l" => "A", "n" => 1),
   
'b' => array("l" => "B", "n" => 2),
   
'c' => array("l" => "C", "n" => 1),
   
'd' => array("l" => "D", "n" => 2),
   
'e' => array("l" => "E", "n" => 2),
);

uasort($a, 'cmp');
print_r($a);

stable_uasort($b, 'cmp');
print_r($b);
?>

returns

Array
(
    [e] => Array
        (
            [l] => E
            [n] => 2
        )

    [b] => Array
        (
            [l] => B
            [n] => 2
        )

    [d] => Array
        (
            [l] => D
            [n] => 2
        )

    [c] => Array
        (
            [l] => C
            [n] => 1
        )

    [a] => Array
        (
            [l] => A
            [n] => 1
        )

)
Array
(
    [b] => Array
        (
            [l] => B
            [n] => 2
        )

    [d] => Array
        (
            [l] => D
            [n] => 2
        )

    [e] => Array
        (
            [l] => E
            [n] => 2
        )

    [a] => Array
        (
            [l] => A
            [n] => 1
        )

    [c] => Array
        (
            [l] => C
            [n] => 1
        )
)

https://bugs.php.net/bug.php?id=53341
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4
alf at prisguide dot no
6 years ago
User "php at clement dot hk" already provided a stable uasort function, but I find this wrapper much shorter and easier to understand:

https://github.com/vanderlee/PHP-stable-sort-functions/blob/master/classes/StableSort.php

function stable_uasort(array &$array, $value_compare_func) {
    $index = 0;
    foreach ($array as &$item) {
        $item = array($index++, $item);
    }
    $result = uasort($array, function($a, $b) use($value_compare_func) {
        $result = call_user_func($value_compare_func, $a[1], $b[1]);
        return $result == 0 ? $a[0] - $b[0] : $result;
    });
    foreach ($array as &$item) {
        $item = $item[1];
    }
    return $result;
}
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4
Anonymous
10 years ago
//this fix the problem of if any of these sort functions evaluates two members as equal then the order is undefined (the sorting is not stable).

$pos=0;
foreach($values as $k => $v)
  $tosort[$k]=array($v,$pos++);
uasort($tosort,function($a, $b) {
  if($a[0] != $b[0])return ($a[0] < $b[0]) ? -1 : 1;
    return ($a[1] < $b[1]) ? -1 : 1;}
);
foreach($tosort as $k => $v)
  $values[$k]=$v[0];
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11
php arobase kochira period com
15 years ago
Difference between uasort() and usort(), the missing example ...

<?php
  $arr
= array ( 10 => array('id' => 'dix''aa' => '1010'),
               
100 => array('id' => 'cent', 'aa' => '100100'),
                 
2 => array('id' => 'deux', 'aa' => '22'),
                 
7 => array('id' => 'sept', 'aa' => '77'));

 
// id sorting
 
function so ($a, $b) { return (strcmp ($a['id'],$b['id']));    }
?>

*** uasort($arr, 'so') output:

<?php Array (
    [
100] => Array
        (
            [
id] => cent
           
[aa] => 100100
       
)

    [
2] => Array
        (
            [
id] => deux
           
[aa] => 22
       
)

    [
10] => Array
        (
            [
id] => dix
           
[aa] => 1010
       
)

    [
7] => Array
        (
            [
id] => sept
           
[aa] => 77
       
))?>

*** usort($arr, 'so') output:

<?php Array (
    [
0] => Array
        (
            [
id] => cent
           
[aa] => 100100
       
)

    [
1] => Array
        (
            [
id] => deux
           
[aa] => 22
       
)

    [
2] => Array
        (
            [
id] => dix
           
[aa] => 1010
       
)

    [
3] => Array
        (
            [
id] => sept
           
[aa] => 77
       
))?>
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7
phire_sk
13 years ago
I tried using some of the previous built multisorts, but they weren't working as expected.

So, I made my own Class, and it seems to work wonderfully.

Here is the code:

<?php
/************************************
*    Allows sorting multi-dimensional
*    arrays by a specific key and in
*    asc or desc order
**/
class multiSort
{
    var
$key;    //key in your array

    //runs the sort, and returns sorted array
   
function run ($myarray, $key_to_sort, $type_of_sort = '')
    {
       
$this->key = $key_to_sort;
       
        if (
$type_of_sort == 'desc')
           
uasort($myarray, array($this, 'myreverse_compare'));
        else
           
uasort($myarray, array($this, 'mycompare'));
           
        return
$myarray;
    }
   
   
//for ascending order
   
function mycompare($x, $y)
    {
        if (
$x[$this->key] == $y[$this->key] )
            return
0;
        else if (
$x[$this->key] < $y[$this->key] )
            return -
1;
        else
            return
1;
    }
   
   
//for descending order
   
function myreverse_compare($x, $y)
    {
        if (
$x[$this->key] == $y[$this->key] )
            return
0;
        else if (
$x[$this->key] > $y[$this->key] )
            return -
1;
        else
            return
1;
    }
}
?>
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2
php at eden2 dot com
20 years ago
Is it just me, or are the examples below misleading, and actually demonstrating situations that would be more appropriate for usort()?

After trying to make sense of the uasort() description, it sounds like it's more for sorting a 1D array like this:

"john" => "$23.12"
"tim" => "$6.50"
"bob" => "$18.54"

and getting back:

"tim" => "$6.50"
"bob" => "$18.54"
"john" => $23.12"

(assuming, of course, that your sort function is lopping off the $ and evaluating as a number -- which would complicate the use of asort() ;)
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1
stilgar_cpsNOSPAM at zipmail dot NOSPAMcom dot br
22 years ago
Use example:

$array[0]['Fator1']=7;
$array[0]['Fator2']="Name";
$array[1]['Fator1']=5;
$array[1]['Fator2']="Name";
$array[2]['Fator1']=7;
$array[2]['Fator2']="NameDiferente";
.....

We want to order by Fator1, then Fator2, then:

function Compare($ar1, $ar2)
{
   if ($ar1['Fator1']<$ar2['Fator1'])
      return -1;
   else if ($ar1['Fator1']>$ar2['Fator1'])
      return 1;
   if ($ar1['Fator2']<$ar2['Fator2'])
      return -1;
   else if ($ar1['Fator2']>$ar2['Fator2'])
      return 1;
   return 0;
}

To sort now, we use:

uasort($array, 'Compare');
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2
iborodikhin at gmail dot com
11 years ago
To shuffle assoc array preserving keys just do this:
<?php uasort(
   
$array,
    function (
$a, $b) {
        return
mt_rand(0, 1) > 0 ? 1 : -1;
    }
);
?>
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2
woodongwong at gmail dot com
3 years ago
PHP version >= 7

<?php

// Comparison function
function cmp($a, $b) {
    return
$a <=> $b;
}

// Array to be sorted
$array = ['a' => 4, 'b' => 8, 'c' => -1, 'd' => -9, 'e' => 2, 'f' => 5, 'g' => 3, 'h' => -4];
print_r($array);

// Sort and print the resulting array
uasort($array, 'cmp');
print_r($array);

?>

PHP version >= 7.4

<?php

// Array to be sorted
$array = ['a' => 4, 'b' => 8, 'c' => -1, 'd' => -9, 'e' => 2, 'f' => 5, 'g' => 3, 'h' => -4];
print_r($array);

// Sort and print the resulting array
uasort($array, fn($a, $b) => $a <=> $b);
print_r($array);

?>
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0
JeffZhang
2 years ago
A stable sort is realized by merging sorting, like "uasort" but stable, and the code is modified based on "mergesort"

<?php

function uamergesort(&$array, $callback = 'strcmp') {
   
$arraycount = count($array);
    if (
$arraycount < 2) {
        return;
    }
   
$halfway = $arraycount / 2;
   
$array1 = array_slice($array, 0, $halfway, true);
   
$array2 = array_slice($array, $halfway, null, true);
   
$this->uamergesort($array1, $callback);
   
$this->uamergesort($array2, $callback);

   
$array = array();
   
$ptr1 = $ptr2 = 0;
   
$array1keys = array_keys($array1);
   
$array1 = array_values($array1);
   
$array2keys = array_keys($array2);
   
$array2 = array_values($array2);
   
$array1count = count($array1);
   
$array2count = count($array2);
    while (
$ptr1 < $array1count && $ptr2 < $array2count) {
        if (
call_user_func($callback, $array1[$ptr1], $array2[$ptr2]) < 1) {
           
$array[$array1keys[$ptr1]] = $array1[$ptr1];
           
$ptr1++;
        } else {
           
$array[$array2keys[$ptr2]] = $array2[$ptr2];
           
$ptr2++;
        }
    }
    while (
$ptr1 < $array1count) {$array[$array1keys[$ptr1]] = $array1[$ptr1]; $ptr1++;}
    while (
$ptr2 < $array2count) {$array[$array2keys[$ptr2]] = $array2[$ptr2]; $ptr2++;}

    return;
}
?>
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0
bpolaszek at gmail dot com
5 years ago
Keep in mind that PHP sorting functions are not reliable to handle "stable sorting", even since PHP7+.
It might work on small arrays, but not on "big" ones (100 items are enough for the stable sorting to fail).

<?php
$a
= array_fill(0, 100, 'foo');
$b = $a;
var_dump($b === $a); // bool(true)

uasort($a, function () {
    return
0; // Consider all items are the same
});

var_dump($b === $a); // bool(false)
?>

To ensure $b === $a, use a 3rd-party stable sorting function:

http://php.net/manual/en/function.uasort.php#121283
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-1
lixuss at gmail dot com
4 years ago
Here is a bug fix for "php at clement dot hk" stable_uasort(&$array, $cmp_function)

The implementation has problems with "0" values, because while() cycle stops on current() returning value "0" which is considered false. The condition must be !== false

Just fix those 3 lines:

while(current($array1) && current($array2)) => while(current($array1)!==false && current($array2)!==false)

while(current($array1)) => while(current($array1)!==false)

while(current($array2)) => while(current($array1)!==false)
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0
ayaou dot mohammed at gmail dot com
7 years ago
// Anonumous functions
uasort($collection, array($this, function($a, $b){
     //logic
}));
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0
paul at webtop-designs dot com
14 years ago
Just expanding on php arobase kochira period com's method:

If you are looking to sort a multi-D array by a specific column and have entries in both upper and lower case, simply drop the entries to lowercase before doing the strcmp.

<?php
$dirs
= array(
  array(
'name' => 'First Folder', 'path' => 'sompath'),
  array(
'name' => 'second folder', 'path' => 'sompath2'),
  array(
'name' => 'Third Folder', 'path' => 'sompath3')
);

function
so($a, $b) {
    return (
strcmp (strtolower($a['name']), strtolower($b['name'])));
}
?>
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0
dholmes at jccc d0t net
21 years ago
Here is a little sort function that actually uses a dynamic callback for usort to do it's thing.

It assumes your data is in the form of:
    $data = array(
            array('ID'=>'6','LAST'=>'Holmes','FIRST'=>'Dan'),
            array('ID'=>'1234','LAST'=>'Smith','FIRST'=>'Agent K'),
            array('ID'=>'2','LAST'=>'Smith','FIRST'=>'Agent J'),
            array('ID'=>'4','LAST'=>'Barney','FIRST'=>'Bob'));

Now, you want to sort on one or more cols, don't you? 

masort($data, 'LAST,FIRST');
or
masort($data,array('FIRST','ID'));

Of course you could add a bunch to it (like numeric comparison if appropriate, desc/asc, etc) but it works for me.

function masort(&$data, $sortby){
    if(is_array($sortby)){
        $sortby = join(',',$sortby);
    }

    uasort($data,create_function('$a,$b','$skeys = split(\',\',\''.$sortby.'\');
        foreach($skeys as $key){
            if( ($c = strcasecmp($a[$key],$b[$key])) != 0 ){
                return($c);
            }
        }
        return($c); '));
}
Notice that I am splitting the string in the comparison function? While this is certainly slower, it was the only way I would find to "pass" and "array".  If anyone has a better way, please suggest.  Then inside, we (string) compare the values only moving to the next key if the values are the same...and so on, and so on.
up
-1
Said Dashuk
12 years ago
My simple and effective solution for sort multi-dimensional array by any key:

<?php
function sort_by_key ($arr,$key) {
    global
$key2sort;
   
$key2sort = $key;
   
uasort($arr, 'sbk');
    return (
$arr);
}
function
sbk ($a, $b) {global $key2sort; return (strcasecmp ($a[$key2sort],$b[$key2sort]));}
?>
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-3
naholyr at yahoo dot fr
21 years ago
You can sort a multidimensionnal array by any of its key with this function:

function multi_sort($array, $key)
{
  $cmp_val="((\$a['$key']>\$b['$key'])?1:
    ((\$a['$key']==\$b['$key'])?0:-1))";
  $cmp=create_function('$a, $b', "return $body;");
  uasort($array, $cmp);
  return $array;
}

example:
$myarray = array(
  array("name"=>"kernighan", "language"=>"c"),
  array("name"=>"lerdorf", "language"=>"php"),
  array("name"=>"Stroustrup", "language"=>"c++"),
  array("name"=>"Gosling", "language"=>"java")
);

multi_sort($myarray, "name") returns:
name=Gosling    language=java
name=Kernighan    language=c
name=Lerdorf    language=php
name=Stroustrup    language=c++
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