uasort

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

uasort — 使用用户自定义的比较函数对数组中的值进行排序并保持索引关联

说明

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

本函数对数组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。

Note:

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。

callback

用户自定义比较函数的例子请参考 usort() 和 uksort()。

返回值

成功时返回 true， 或者在失败时返回 false。

范例

Example #1 uasort() 的基本例子

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

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

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

以上例程会输出：

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

User Contributed Notes

JeffZhang 11-Aug-2021 06:39
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;
}
?>
woodongwong at gmail dot com 29-Oct-2020 01:38
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);

?>
lixuss at gmail dot com 14-Mar-2020 05:35
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)
bpolaszek at gmail dot com 19-Jun-2018 01:47
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
alf at prisguide dot no 28-Jun-2017 11:44
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 $result;
}
ayaou dot mohammed at gmail dot com 15-Jun-2016 03:05
// Anonumous functions
uasort($collection, array($this, function($a, $b){
     //logic
}));
php at clement dot hk 04-Mar-2014 04:00
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
Anonymous 15-Aug-2013 10:35
//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];
iborodikhin at gmail dot com 22-Nov-2012 08:32
To shuffle assoc array preserving keys just do this:
<?php uasort(
    $array,
    function ($a, $b) {
        return mt_rand(0, 1) > 0 ? 1 : -1;
    }
); ?>
Said Dashuk 11-Oct-2011 10:33
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]));}
?>
yannick dot battail at gmail dot com 17-Nov-2010 06:37
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
)
magikMaker 19-Oct-2010 02:48
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'));

?>
phire_sk 05-Oct-2010 02:19
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;
    }
}
?>
paul at webtop-designs dot com 30-Nov-2009 01:40
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'])));
}
?>
php arobase kochira period com 08-Jun-2008 04:13
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
        ))?>
php at eden2 dot com 17-Jul-2003 04:36
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() ;)
naholyr at yahoo dot fr 10-Jan-2003 09:35
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++
dholmes at jccc d0t net 09-Oct-2002 02:27
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.
stilgar_cpsNOSPAM at zipmail dot NOSPAMcom dot br 05-Sep-2001 02:30
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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