iterate reverse over php associative array

Question

How does one iterate in reverse over php associative array? https://stackoverflow.com/a/10777617/1032531 gives solutions for a non-associated array.

My attempt:

$a=['5'=>'five','3'=>'three','7'=>'seven'];
var_dump($a);
foreach($a as $k=>$v){echo("$k $v\n");}
$a=array_reverse($a);
var_dump($a);
foreach($a as $k=>$v){echo("$k $v\n");}

produces the following results:

array(3) {
  [5]=>
  string(4) "five"
  [3]=>
  string(5) "three"
  [7]=>
  string(5) "seven"
}
5 five
3 three
7 seven
array(3) {
  [0]=>
  string(5) "seven"
  [1]=>
  string(5) "three"
  [2]=>
  string(4) "five"
}
0 seven
1 three
2 five

I wish to preserve the keys, and return:

array(3) {
  [5]=>
  string(4) "five"
  [3]=>
  string(5) "three"
  [7]=>
  string(5) "seven"
}
5 five
3 three
7 seven
array(3) {
  [7]=>
  string(5) "seven"
  [3]=>
  string(5) "three"
  [5]=>
  string(4) "five"
}
7 seven
3 three
5 five

Why not use array_reverse and iterate over?

Sachin Gadagi
– Sachin Gadagi

2016-07-06 13:24:02 +00:00
Commented Jul 6, 2016 at 13:24 — Sachin Gadagi
– Sachin Gadagi, Commented Jul 6, 2016 at 13:24

Alexis · Accepted Answer · 2016-07-06 13:26:14Z

9

Just use $a=array_reverse($a,true); instead of $a=array_reverse($a); for keep key.

array_reverse() have a second optional parameter for preserve keys. default value is false.

Read doc here

edited Jul 6, 2016 at 13:26

answered Jul 6, 2016 at 13:23

Alexis

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1 Comment

user1032531 Over a year ago

Perfect! Thank you

IMSoP · Accepted Answer · 2016-07-06 13:24:41Z

2

You were very close - you had all the key words already - and just need to remember that the PHP manual is your friend :)

The manual page for array_reverse lists an optional argument $preserve_keys, which defaults to false.

So you just need to change $a=array_reverse($a); to $a=array_reverse($a, true);, and you should get the result you were after.

answered Jul 6, 2016 at 13:24

IMSoP

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