How to Modify Array Values in a PHP Foreach Loop: Reference or Key?

Modifying Array Values within a Foreach Loop

In PHP, it is possible to modify the current object being handled within a foreach loop. To do so, there are two primary approaches:

Using a Loop Variable with Array Key:

<?php
foreach($questions as $key => $question){
    $questions[$key]['answers'] = $answers_model->get_answers_by_question_id($question['question_id']);
}
?>

Here, we iterate over the $questions array using a loop variable ($key) that represents the array index. By explicitly updating the $questions array at the corresponding index ($key), we effectively modify the original object.

Using a Reference:

<?php
foreach($questions as &$question){
    $question['answers'] = $answers_model->get_answers_by_question_id($question['question_id']);
}
?>

In this case, we add an ampersand (&) before the loop variable ($question), which passes a reference to the object. By modifying the object through the reference, we directly update the object in the original $questions array.

Which Approach is Recommended?

While both approaches work, using a loop variable with array key is generally preferred. This is because it explicitly updates the original array, making it easier to track modifications for debugging or further processing.

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