php change specific value of nested array item [duplicate] - php

Question

This question already has answers here:
How to modify an array's values by a foreach loop?
(2 answers)
Closed 4 months ago.
I was wondering if it is possible to edit the current object that's being handled within a foreach loop
I'm working with an array of objects $questions and I want to go through and look for the answers associated with that question object in my db. So for each question go fetch the answer objects and update the current $question inside my foreach loop so I can output/process elsewhere.
foreach($questions as $question){
$question['answers'] = $answers_model->get_answers_by_question_id($question['question_id']);
}

Answer 1

There are 2 ways of doing this
foreach($questions as $key => $question){
$questions[$key]['answers'] = $answers_model->get_answers_by_question_id($question['question_id']);
}
This way you save the key, so you can update it again in the main $questions variable
or
foreach($questions as &$question){
Adding the & will keep the $questions updated. But I would say the first one is recommended even though this is shorter (see comment by Paystey)
Per the PHP foreach documentation:
In order to be able to directly modify array elements within the loop precede $value with &. In that case the value will be assigned by reference.

Answer 2

Surely using array_map and if using a container implementing ArrayAccess to derive objects is just a smarter, semantic way to go about this?
Array map semantics are similar across most languages and implementations that I've seen. It's designed to return a modified array based upon input array element (high level ignoring language compile/runtime type preference); a loop is meant to perform more logic.
For retrieving objects by ID / PK, depending upon if you are using SQL or not (it seems suggested), I'd use a filter to ensure I get an array of valid PK's, then implode with comma and place into an SQL IN() clause to return the result-set. It makes one call instead of several via SQL, optimising a bit of the call->wait cycle. Most importantly my code would read well to someone from any language with a degree of competence and we don't run into mutability problems.
<?php
$arr = [0,1,2,3,4];
$arr2 = array_map(function($value) { return is_int($value) ? $value*2 : $value; }, $arr);
var_dump($arr);
var_dump($arr2);
vs
<?php
$arr = [0,1,2,3,4];
foreach($arr as $i => $item) {
$arr[$i] = is_int($item) ? $item * 2 : $item;
}
var_dump($arr);
If you know what you are doing will never have mutability problems (bearing in mind if you intend upon overwriting $arr you could always $arr = array_map and be explicit.