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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 0.99 和 0.1 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

usort() - 使用用户自定义的比较函数对数组中的值进行排序
uksort() - 使用用户自定义的比较函数对数组中的键名进行排序
数组排序函数对比

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User Contributed Notes 20 notes

down

146

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'));



?>

down

yannick dot battail at gmail dot com ¶

12 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
)

down

php at clement dot hk ¶

9 years ago

down

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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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
        ))?>

down

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];

down

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;

    }

}

?>

down

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() ;)

down

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');

down

iborodikhin at gmail dot com ¶

10 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;

    }

); ?>

down

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);

?>

down

tschallacka at lookingout dot com ¶

2 years ago

php > 7

Sorting associative array, by a value of a subarray.

<?php
uasort($items, function ($a, $b) {
   if ($a['sort_order']??0 == $b['sort_order']??0) {
      return 0;
   }
   return ($a['sort_order']??0 < $b['sort_order']??0) ? -1 : 1;
});
?>

down

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;
}
?>

down

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

down

-1

lixuss at gmail dot com ¶

3 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)

down

paul at webtop-designs dot com ¶

13 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'])));

}

?>

down

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.

down

-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]));}

?>

down

-1

ayaou dot mohammed at gmail dot com ¶

7 years ago

// Anonumous functions
uasort($collection, array($this, function($a, $b){
     //logic
}));

down

-5

naholyr at yahoo dot fr ¶

20 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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