iteratively / programmatically replace a value in a multidimensional array (in Codeigniter or PHP)

Question

I have found several purported solutions to this question, but when I try and implement them, they do not work.

$a = array('val'=>10, 'name'=>'Name of A', 'item3'=>'item3forA');
$b = array('val'=>20, 'name'=>'Name of B', 'item3'=>'item3forB');
$c = array('val'=>30, 'name'=>'Name of C', 'item3'=>'item3forC');
$d = array('val'=>40, 'name'=>'Name of D', 'item3'=>'item3forD');
$rlist = array($a, $b, $c, $d);

I need a way to recursively / iteratively replace the value of the 'val' key to make them all a zero (0) value.

Two of the many solutions I have tried are here and here. I will also note if I 'explicitly' set the key to zero $a['val']=0; $b['val']=0; etc., that works, but I would rather set it to zero with less code (the actual program has like 20 multi-dimensional arrays to modify).

Just loop and assign. Make sure you edit the same copy of the subarray. — mighty_dev
– mighty_dev, Commented Oct 22, 2020 at 13:58
Can you share more details? What have you tried so far? Where are you stuck? — Nico Haase
– Nico Haase, Commented Oct 22, 2020 at 14:04

Don't Panic · Accepted Answer · 2020-10-22 14:34:37Z

1

PHP does assignment by value unless explicitly instructed otherwise, so when you do

$rlist = array($a, $b, $c, $d);

The inner arrays of $rlist will be the values of $a, $b, $c, and $d, not references to those actual variables. So if you're iterating over $rlist and modifying its values, you will not see those changes reflected in the original $a, $b, etc. variables.

If you need that to happen, you can assign those variables to $rlist by reference as well as using a reference when you iterate $rlist as shown in the other answer.

$rlist = array(&$a, &$b, &$c, &$d);

Other possibilities you may consider based on how they fit in with the rest of your code are

assigning the values of $a, etc. directly to $rlist['a'], etc. at the point where you're currently defining them as individual variables
using stdClass objects (or instances of a class you define) instead of arrays, which will not need to be assigned by reference to $rlist

edited Oct 22, 2020 at 14:34

answered Oct 22, 2020 at 14:25

Don't Panic

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1 Comment

Robert West Over a year ago

That did it! Thank you so much! :) This $rlist modification, in conjunction with @JitendraYadav's foreach loop is the solution.

Dark Knight · Accepted Answer · 2020-10-22 14:01:23Z

1

Use the reference of the given array and just set val = 0.

foreach($rlist as &$data){
  $data['val'] = 0;
}

answered Oct 22, 2020 at 14:01

Dark Knight

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3 Comments

Robert West Over a year ago

This code is not working. I understand this code, and believe it should work, but it just doesn't. It should not matter if I am trying to do this within an 'if' statement, right?

Dark Knight Over a year ago

I changed your question, you should define $a, $b, $c, $d first and then assign them to $rlist.

Robert West Over a year ago

I understand your edit. Makes sense, and that is what I am doing. Thank you.

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