Creating a fresh, re-indexed array from a source array without using foreach in PHP

Question

I've created a import script to convert a spreadsheet containing vehicle makes and models into related database entities. My source array from the spreadsheet looks like this (each is a spreadsheet row):

$rows = [
    ['Brand A', 'Model A'],
    ['Brand A', 'Model A'],
    ['Brand A', 'Model B'],
    ['Brand A', 'Model B'],
    ['Brand A', 'Model B'],
    ['Brand A', 'Model C'],
    ['Brand B', 'Model A'],
    ['Brand B', 'Model B'],
    ['Brand B', 'Model B'],
    ['Brand B', 'Model B'],
    ['Brand B', 'Model C'],
    ['Brand B', 'Model C'],
];

I want this data in this format:

$data = [
    'Brand A' => [
        'Model A',
        'Model A',
        'Model B',
        'Model B',
        'Model B',
        'Model C',
    ],
    'Brand B' => [
        'Model A',
        'Model B',
        'Model B',
        'Model B',
        'Model C',
        'Model C',
    ],
];

I have a working example using a foreach loop:

$data = [];
foreach ($rows as $row) {
    $data[strval($row[0])][] => strval($row[1]);
}

I'd like to use one of the PHP array functions if possible. I've tried the following but it's not creating the brand name indexes:

$data = array_map(function ($row) {
    return $data[strval($row[0])][] = strval($row[1]);
}, $rows);

The array ends up as follows:

$data = [
    'Model A',
    'Model A',
    ...
];

Is this possible or am I wasting my time/over engineering this?

PT 2: Bonus points for making the models unique for a brand at the same time.

$data = [
    'Brand A' => [
        'Model A',
        'Model B',
        'Model C',
    ],
    'Brand B' => [
        'Model A',
        'Model B',
        'Model C',
    ],
];

Stephan van Leeuwen · Accepted Answer · 2018-06-06 14:08:13Z

9

one way would be to use array_reduce like this

$data = array_reduce($rows, function ($acc, $row) {
    $acc[$row[0]][] = $row[1];
    return $acc;
}, []);

to make the subarrays unique you can use a combination of array_map and array_unique afterwards

$data = array_map(function ($subarr) {
    return array_unique($subarr);
}, $data);

answered Jun 6, 2018 at 14:08

Stephan van Leeuwen

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2 Comments

Frédéric Clausset Over a year ago

+1 because your solution answer the question without a loop as per requested. But I would not use this solution, it is quite too much complicated.Nearly obsfucation here :-)

OK sure Over a year ago

Nice! Thanks Stephan

delboy1978uk · Accepted Answer · 2018-06-06 14:19:36Z

0

I honestly think this is over engineering things.

However, I'm going for the bonus point here!

$new = [];
foreach ($rows as $row) {
    $new[$row[0]][] = $row[1];
    $new[$row[0]] = array_unique($new[$row[0]]);
}

answered Jun 6, 2018 at 14:19

delboy1978uk

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8 Comments

Someone Over a year ago

Doesn't meet the "no loops" criteria. Nice answer, though.

delboy1978uk Over a year ago

Yes I know. :-P The guys answer below does, but as you can see it is MORE code and harder to tell what is going on, which is why I wouldn't do it that way unless it was faster over a million iteration benchmark

OK sure Over a year ago

It does read harder but the problem with loops for me is they end up everywhere in controllers, listeners - even in other loops. So I'll put these iterators into smaller classes and methods, slap some tests on them and they're golden.

delboy1978uk Over a year ago

You shouldn't have any logic in a controller action. a controllers job is to get data from the request and pass it to a service, get the result, and pass it to a view, and handle any expected exceptions, that's it. Sticking your methods in a separate class is the right thing to do, but make a service class, and call that from the controller so your actions are super tidy and the business logic isn't mixed with framework code

OK sure Over a year ago

@delboy1978uk exactly. These are going into an import service to be used in a symfony sonata admin class. Debatable, but I think logic in extended vendor classes is worse than in controllers. At least with a controller you are in control (even though it's terrible). If the vendor adds a protected/public method that causes a collision, or just changes something that some of your extended functionality uses you're either stuck at a version or facing a potentially non-trivial refactor.

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