array_replace
Here are a couple of routines to swap the order of two elements in an array
<?php
function array_swap_forward($arr,$elem)
{
$ndx = array_search($elem,$arr) - 1;
$b4 = array_slice($arr,0,$ndx);
$mid = array_reverse(array_slice($arr,$ndx,2));
$after = array_slice($arr,$ndx + 2);
return array_merge($b4,$mid,$after);
}
function array_swap_back($arr,$elem)
{
$ndx = array_search($elem,$arr);
$b4 = array_slice($arr,0,$ndx);
$mid = array_reverse(array_slice($arr,$ndx,2));
$after = array_slice($arr,$ndx + 2);
return array_merge($b4,$mid,$after);
}
$arr =array('a','b','c','d','e','f');
print_r(array_swap_forward($arr,'c'));
echo '<br>';
print_r(array_swap_back($arr,'c'));
?>
array_reverse
(PHP 4, PHP 5)
array_reverse — 要素を逆順にした配列を返す
説明
array array_reverse
( array
$array
[, bool $preserve_keys = false
] )配列を受け取って、要素の順番を逆にした新しい配列を返します。
パラメータ
-
array -
入力の配列。
-
preserve_keys -
TRUEの場合は数値のキーを保持します。 非数値のキーは、この設定にかかわらず常に保持されます。
返り値
逆転させた配列を返します。
変更履歴
| バージョン | 説明 |
|---|---|
| 4.0.3 |
パラメータ preserve_keys が追加されました。
|
例
例1 array_reverse() の例
<?php
$input = array("php", 4.0, array("green", "red"));
$reversed = array_reverse($input);
$preserved = array_reverse($input, true);
print_r($input);
print_r($reversed);
print_r($preserved);
?>
上の例の出力は以下となります。
Array
(
[0] => php
[1] => 4
[2] => Array
(
[0] => green
[1] => red
)
)
Array
(
[0] => Array
(
[0] => green
[1] => red
)
[1] => 4
[2] => php
)
Array
(
[2] => Array
(
[0] => green
[1] => red
)
[1] => 4
[0] => php
)
add a note
User Contributed Notes
array_reverse - [7 notes]
atulmvAThotmailDOTcoDOTuk ¶
8 months ago
alfbennett at gmail dot com ¶
3 years ago
Needed to just reverse keys. Don't flog me if there is a better way. This was a simple solution.
<?php
function array_reverse_keys($ar){
return array_reverse(array_reverse($ar,true),false);
}
?>
rahulavhad at yahoo dot com ¶
12 years ago
This code can help in recursive reversing of the array...
<?php
$arr1 = array(2,1,array(5,2,1,array(9,8,7)),5,0);
$arr1 = array_reverse($arr1);
function Reverse_Array($array)
{ $index = 0;
foreach ($array as $subarray)
{ if (is_array($subarray))
{ $subarray = array_reverse($subarray);
$arr = Reverse_Array($subarray);
$array[$index] = $arr;
}
else {$array[$index] = $subarray;}
$index++;
}
return $array;
}
$arr2 = Reverse_Array($arr1);
?>
Anonymous ¶
8 days ago
<?php
$arr=array(1,2,3,4,5,6,7,8,9);
function ArrayRev($arr){
$a=count($arr);
for($i=$a-1;$i>=0;$i--){
$n[]=$arr[$i];
}
return $n;
}
print_r(ArrayRev($arr));
?>
//output Array ( [0] => 9 [1] => 8 [2] => 7 [3] => 6 [4] => 5 [5] => 4 [6] => 3 [7] => 2 [8] => 1 )
david at audiogalaxy dot com ¶
13 years ago
With associative arrays array_reverse() keeps key => value pairs matched but reverses the order of the array as spaned by functions like each(). With numerical indexes array_reverse not only reverses position (as spaned by each) but also renumbers the keys.
Both cases seem to be what people would generally want: indeed without the renumbering behavior, someone refering to array elements by numerical key wouldn't think array_reverse did anything.
However, people who are trying to keep numerical keys associated with their values - e.g. trying to have holes in their arrays - will be foiled by the renumbering. The most telling results come from applying array_reverse() to arrays with mixed keys (some numbers and some strings). The strings stay attached and the rest of the keys get renumbered around them - most annoying if you are thinking what you've got is an associative array but some of your keys happen to be numbers.
david at audiogalaxy dot com ¶
13 years ago
As a further clarification: key-value pairs have an order within an array completely separate from whatever the keys happen to be - the order in which you add them. This is the order that functions like each() and next() will move their pointer through the array.
If you add to an array without specifying the key, like $array[] = value; then an internal counter supplies the key value and then the numerical order of your keys will be identical to the the internal order. If you "leave holes" - jumping ahead by specifying a higher number for the key, like $array[1000] = value; the internal counter gets pushed forward appropriately. Other than its effect on this internal counter, specifying a numerical key seems no different than specifying a string.
However, some array functions, like array_merge() and array_reverse() treat keys that are numbers differently from keys that are not.
virtual89 at gmail dot com ¶
9 months ago
With array_reverse() if the keys are strings, they remain the same, example:
<?php
$a = array ("zero"=>"hello","one"=>"world");
var_dump (array_reverse($a));
?>
Outputs:
array(2) {
["one"]=>
string(5) "world"
["zero"]=>
string(5) "hello"
}
But if the keys are numbers, they will be changed starting from 0, example:
<?php
$a = array (10=>"hello",20=>"world");
var_dump (array_reverse($a));
?>
Outputs:
array(2) {
[0]=>
string(5) "world"
[1]=>
string(5) "hello"
}