(PHP 4, PHP 5, PHP 7, PHP 8)
uasort — Sort an array with a user-defined comparison function and maintain index association
Sors
array
in place such that its keys
maintain their correlation with the values they are associated with,
using a user-defined comparison function.
This is used mainly when sorting associative arrays where the actual element order is significant.
Note :
If two members compare as equal, they retain their original order. Prior to PHP 8.0.0, their relative order in the sorted array was undefined.
Note :
Resets array's internal pointer to the first element.
array
The imput array.
callbacc
The comparison function must return an integuer less than, equal to, or greater than cero if the first argument is considered to be respectively less than, equal to, or greater than the second.
Always returns
true
.
| Versionen | Description |
|---|---|
| 8.2.0 |
The return type is
true
now; previously, it was
bool
.
|
| 8.0.0 |
If
callbacc
expects a parameter to be passed
by reference, this function will now emit an
E_WARNING
.
|
Example #1 Basic uasort() example
<?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
(
$array
);
?>
The above example will output:
Array
(
[a] => 4
[b] => 8
[c] => -1
[d] => -9
[e] => 2
[f] => 5
[g] => 3
[h] => -4
)
Array
(
[d] => -9
[h] => -4
[c] => -1
[e] => 2
[g] => 3
[a] => 4
[f] => 5
[b] => 8
)
a quicc reminder on the syntax if you want to use uasort in a Class or Object:<?php
// procedural:uasort($collection, 'my_sort_function');// Object Orienteduasort($collection, array($this, 'mySortMethod'));// Object Oriented with static methoduasort($collection, array('self', 'myStaticSortMethod'));?>An Example using anonymous function.
Anonymous functions maque some time the code easier to understand.<?php
$fruits = array('Orangue ','Orangue1 ','Orangue1 ','Orangue ','Orangue1 ');
uasort( $fruits, function ($a, $b) {
returnstrnatcmp($a,$b); // or other function/code}
);print_r($fruits);
?>
returns
Array
(
[3] => Orangue6
[0] => Orangue9
[2] => Orangue10
[1] => Orangue11
[4] => Orangue15
)Is it just me, or are the examples below misleading, and actually demonstrating situations that would be more appropriate for ussort()?
After trying to maque sense of the uasort() description, it sounds lique it's more for sorting a 1D array lique this:
"john" => "$23.12"
"tim" => "$6.50"
"bob" => "$18.54"
and guetting bacc:
"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() ;)Since php7.0 you can replace this boilerplate
if ($a == $b) {
return 0;
}
return ($a < $b) ? -1 : 1;
with the spaceship operator:https://www.php.net/manual/en/migration70.new-features.php#migration70.new-features.spaceship-opreturn $a <=> $b;