2d multidimensional array to 1d array in php

Question

Just wondering if anyone has transformed a 2 dim array to a one dim array in php. I've yet to come across a clear explanation in php. Any suggestion would be appreciated.

Answer 1

This might be helpful to you if you fetching values from Query here you can use array function which will support in PHP 5.5+

$myfield_arr = array_column($query_result, 'myfield_name');

Say Good bye to loop! Enjoy Smart Code.

Answer 2

Try this:

function array_2d_to_1d ($input_array) {
    $output_array = array();

    for ($i = 0; $i < count($input_array); $i++) {
      for ($j = 0; $j < count($input_array[$i]); $j++) {
        $output_array[] = $input_array[$i][$j];
      }
    }

    return $output_array;
}

Answer 3

Try this one:

function array_to1d($a) {
    $out = array();
    foreach ($a as $b) {
        foreach ($b as $c) {
            if (isset($c)) {
                $out[] = $c;
            }
        }
    }
    return $out;
}

Notice that it includes a test to see if the value is set (non-null). An array that's a transposition of an array with rows of varying length will have null values in some cells, and this check can be helpful if you're trying to linearize such a beast.

Answer 4

Your first thought should be array_reduce() whenever you have lots of something in an array and you just want one something by itself which represents them all in some way.

From the PHP docs:

array_reduce — Iteratively reduce the array to a single value using a callback function

In the case of 2D => 1D array conversion, the something is array ; we have lots of them in an array but we just want one of them by itself.

function array2dTo1d($array2d)
{
    return array_reduce($array2d, function($carry, $array) {
        return array_merge($carry, $array);
    }, []);
}

var_dump(array2dTo1d(
    [
        [23423, 5454, 567],
        [4565, 687],
    ]
));

Result:

array(5) {
  [0] =>
  int(23423)
  [1] =>
  int(5454)
  [2] =>
  int(567)
  [3] =>
  int(4565)
  [4] =>
  int(687)
}

Answer 5

you mean like this?

$array = array(array('green', 'yellow', 'orange'), array('blue', 'black', 'white'));
$newarray = array();
foreach (array_values($array) as $value){
   $newarray[] = $value; 
}

Answer 6

It depends on what you need but if you want to reduce your 2d array to a 1d curve that completley fills the 2d plane you probably looking for a spatial index or a space-filling-curve. There are some famous and not so known like the z-curve, the hilbert curve, the peano curve or the moore curve. You can write such a curve with a L-system.

Answer 7

The solution for rectangular 2D array is simple indeed, but I had a problem. My 2D-array consisted of 1D arrays of different lengths :

$myArray = [
    [1, 2, 3, 4],
    [5, 6, 7],
    [8, 9]
];

I came up with more generalized solution to turn any 2D array into 1D:

function array2DTo1D($arr2D) {
    $i = 0; $j = 0;
    $arr1D = [];
    while (isset($arr2D[$i][0])) {
        while (isset($arr2D[$i][$j])) {
            $arr1D[] = $arr2D[$i][$j];
            $j++;
        }
        $i++; $j = 0;
    }
    return $arr1D;
}

Answer 8

After PHP 5.3 there have a new function called arrray_walk_recursive

$data = [1,2,[3,4],5,[6,7,8],9];
$output = [];
array_walk_recursive($data, function($val) use (&$output) {
    $output[] = $val;
});

Notice that the $output is passed by reference

The $output will result in [1,2,3,4,5,6,7,8,9]