Question

I want to convert this.

$data1 = array(
    array('value' => '100.00', 'total' => '32'),
    array('value' => '10.00', 'total' => '13'),
    array('value' => '200.00', 'total' => '39'),
    array('value' => '190.00', 'total' => '11'),
);

into this

$data2 = array(
    'value' => array(0 => '100.00', 1 => '10.00', 2 => '200.00', 3 => '190.00'),
    'total' => array(0 => '32', 1 => '13', 2 => '39', 3 => '11')
);

I can obviously do this in a roundabout way by iterating over the top array, while appending to a series of arrays, but I figured that there must be a php array function that I don’t know about that can do this more concisely.

http://www.php.net/manual/en/ref.array.php

Values are floats and integers (if it makes any difference), I’ve just added them as strings in the example code because it’s easier to read IMO. Final array order should match the initial order. I’ll award the correct answer to the least LOC providing performance isn’t significantly worse that the ‘long’ version. PHP 5.4.

Answer 1

<?php // php 5.4 array syntax

$new = array_reduce($data1, function (&$result, $item)
    {
        $result['value'][] = $item['value'];
        $result['total'][] = $item['total']; 
        return $result;
    },
    ['value' => [], 'total' => []]);

‘value’ and ‘total’ are arbitrary names, so you’re not going to get a one-liner php library function to do this.

You can refactor this code into a function if you want to…

function array_rotate($data) {
    $k = array_keys($data[0]);
    return array_reduce($data, function (&$r, $i) use ($k) {
        $r[$k[0]][] = $i[$k[0]];
        $r[$k[1]][] = $i[$k[1]]; 
        return $r;
    }, [$k[0] => [], $k[1] => []]);
}

I generalised @matthew’s code, this allows an arbitrary number of keys (instead of 2):

function array_rotate2($data) {
    return array_combine(array_keys($data[0]), 
        array_map(function ($field) use ($data) {
              return array_map(function($row) use ($field) { return $row[$field]; }, $data);
            }, array_keys($data[0])));
}