Populating associative array values from other arrays in PHP

Question

If I have separate arrays w/ values for "questions" and "answers" like so:

var_dump($questions)

array (size=2)
  0 => string 'Question 1' (length=10)
  1 => string 'Question 2' (length=10)

var_dump($answers)

array (size=2)
  0 => string 'Answer 1' (length=10)
  1 => string 'Answer 2' (length=10)

How can I use these arrays to populate the values of a "master" associative array w/ keys for "question" and "answer" so I can then use a foreach loop to easily output the question/answer pairs? I'm trying to loop over each of the $questions and $answers arrays to populate values of a $results array- I've tried

foreach ( $questions as $question ) {
    $results[] = ['question' => $question];
}

and this creates separate items for each question, but I'm not sure how to add the "answer" values into the same array items to create the pairs. Thank you for any assistance here.

This question does not have a clear [mcve] because you didn't explicitly state the desired output structure from the sample input. Mentioning "tips" after receiving an answer is not helpful to the page and usually wastes volunteers' time by forcing them to refactor their advice. — mickmackusa, May 06 '22 at 03:06
If you are seeking data transposition [Demo](https://3v4l.org/V1OPg), we have a canonical page for that too. [Dupe target](https://stackoverflow.com/q/797251/2943403) — mickmackusa, May 06 '22 at 03:07

Alex Howansky · Accepted Answer · 2022-05-05T17:02:59.173

Not sure I'm understanding the question correctly, but the array_combine() function may do what you want.

$master = array_combine($questions, $answers);

This will give you:

[
    'question 1' => 'answer 1',
    'question 2' => 'answer 2',
    'question 3' => 'answer 3',
]

Then you can do:

foreach ($master as $question => $answer) {
    ...
}

Note, this implies that questions are unique.

If instead, you want an indexed array of associative arrays, you could do something like:

$master = [];
foreach (array_combine($questions, $answers) as $question => $answer) {
    $master[] = [
        'question' => $question,
        'answer' => $answer,
    ];
}

This will give you:

[
    [
        'question' => 'question 1',
        'answer' => 'answer 1',
    ],
    [
        'question' => 'question 2',
        'answer' => 'answer 2',
    ],
    [
        'question' => 'question 3',
        'answer' => 'answer 3',
    ],
]

Or, more traditionally:

$master = [];
for ($i = 0; $i < count($questions); $i++) {
    $master[] = [
        'question' => $questions[$i],
        'answer' => $answers[$i],
    ]
}

This is great- thank you @alex-howansky; `array_combine` looks to be what I was missing. One other question- if I have a third element to add for each- e.g. "tip" ($tips) so each item would have a "question", "answer" and "tip", how would that affect the `array_combine` loop in your answer? — nickpish, May 05 '22 at 17:11
Since the key => value nature of an associative array implies a pair (i.e., just two data items), you couldn't use array_combine -- you'd have to use the for() loop as shown in the 3rd example. — Alex Howansky, May 05 '22 at 17:15

Populating associative array values from other arrays in PHP

1 Answers1