Hierarchical Array Conversion to Flat Array

Question

I've got an array

$array = array(
    array(1,2,3),
    array('bob','bill'),
    array(4,5,6,7) 
    //can have between 0 and 5 "rows"
);

I want to convert to an array that looks like this...

[1,bob,4, 1, bob, 5, 1, bob, 6, 1, bob, 7, 1, bill, 4 .... 3, bill, 7]

I was trying to write a recursive function for this which looks like...

function GetValues($array, $rowIndex, $valIndex, $values)
{
    if(!isset($array[$rowIndex]))
    {
        return $values;
    }
    if(!isset($array[$rowIndex][$valIndex]))
    {
        return GetValues($array,$rowIndex+1, 0, $values);
    }
    $values[] = $array[$rowIndex][$valIndex];

    return  GetValues($array,$rowIndex, $valIndex+1, $values);
}

which just ends up iterating the array normally (prints 1,2,3,bob,bill,4,5,6,7)

`$flatArray = call_user_func_array('array_merge', $array);` – splash58 Jun 10 '16 at 20:10 — splash58, Jun 10 '16 at 20:10

score 2 · Accepted Answer · answered Jun 10 '16 at 20:32

$array = array(
    array(1,2,3),
    array('bob','bill'),
    array(4,5,6,7) 
);
function combinations($arrays) {
    $result[] = array();
    foreach ($arrays as $key => $values) {
        $tmp = array();
        foreach ($result as $result_item) {
            foreach ($values as $value) {
                $tmp[] = array_merge($result_item, array($key => $value));
            }
        }
        $result = $tmp;
    }

    return $result;
}
$combinations_array = combinations($array);
$flat_string = '';
$flat_array = array();
foreach($combinations_array as $value){
        foreach($value as $v){
            $flat_string.=$v.',';
            $flat_array[]=$v;
        }
    }

echo rtrim($flat_string,',');
print_r($flat_array);

Out Put string: 1,bob,4,1,bob,5,1,bob,6,1,bob,7,1,bill,4,1,bill,5,1,bill,6,1,bill,7,2,bob,4,2,bob,5,2,bob,6,2,bob,7,2,bill,4,2,bill,5,2,bill,6,2,bill,7,3,bob,4,3,bob,5,3,bob,6,3,bob,7,3,bill,4,3,bill,5,3,bill,6,3,bill,7

Output array:

    Array
(
    [0] => 1
    [1] => bob
    [2] => 4
    [3] => 1
    [4] => bob
    [5] => 5
    [6] => 1
    [7] => bob
    [8] => 6
    [9] => 1
    [10] => bob
    [11] => 7
    [12] => 1
    [13] => bill
    [14] => 4
    [15] => 1
    [16] => bill
    [17] => 5
    [18] => 1
    [19] => bill
    [20] => 6
    [21] => 1
    [22] => bill
    [23] => 7
    [24] => 2
    [25] => bob
    [26] => 4
    [27] => 2
    [28] => bob
    [29] => 5
    [30] => 2
    [31] => bob
    [32] => 6
    [33] => 2
    [34] => bob
    [35] => 7
    [36] => 2
    [37] => bill
    [38] => 4
    [39] => 2
    [40] => bill
    [41] => 5
    [42] => 2
    [43] => bill
    [44] => 6
    [45] => 2
    [46] => bill
    [47] => 7
    [48] => 3
    [49] => bob
    [50] => 4
    [51] => 3
    [52] => bob
    [53] => 5
    [54] => 3
    [55] => bob
    [56] => 6
    [57] => 3
    [58] => bob
    [59] => 7
    [60] => 3
    [61] => bill
    [62] => 4
    [63] => 3
    [64] => bill
    [65] => 5
    [66] => 3
    [67] => bill
    [68] => 6
    [69] => 3
    [70] => bill
    [71] => 7
)

This answer is missing its educational explanation. Without an explanation, this page is less likely to help future researchers and is not a good candidate to close future questions. — mickmackusa, Aug 30 '21 at 03:54

kainaw · Answer 2 · 2016-06-11T11:11:37.093

0

A problem you will likely have is not knowing how big the original array is. You can write it recursively by destroying the array. In this example, I shift the first element off the original array. Then, with each recursive call, I shift off another element. I use a for loop to go through the values and return what I've built.

function flatten($array)
{
    if(sizeof($array)==0) return null;
    $first = array_shift($array);
    $ret = array();
    foreach($first as $value)
    {
        $ret[] = $value;
        $sub = flatten($array);
        if($sub != null)
            $ret = array_merge($ret, $sub);
    }
    return $ret;
}

edited Jun 11 '16 at 11:11

answered Jun 10 '16 at 19:51

kainaw

4,256
1
18
38

I'll give it a try. The fact the array is destroyed wont be an issue, i can just copy it before calling the function – EyeOfTheHawks Jun 10 '16 at 19:51
I didn't pass by reference in the function, so it will copy the array and destroy the copy. Technically, it will copy the whole array, then the array with one element missing, then that array with one element missing, etc... – kainaw Jun 10 '16 at 19:53
Is it possible to have the function return an array as specified in the question? I tried rigging it up, but the blank string is a bit awkward – EyeOfTheHawks Jun 10 '16 at 19:56
It prints "1,bob,4,5,6,7,bill,4,5,6,7,2,bob,4,5,6,7,bill,4,5,6,7,3,bob,4,5,6,7,bill,4,5,6,7,". – Jose Manuel Abarca Rodríguez Jun 10 '16 at 19:58
Thanks for the edit. I was really close in my edit haha – EyeOfTheHawks Jun 10 '16 at 19:59
I did a quick edit (untested) that makes it an array instead of a string. – kainaw Jun 10 '16 at 19:59
@kainaw Warning: array_merge(): Argument #2 is not an array – EyeOfTheHawks Jun 10 '16 at 20:00
It is complaining because the recursion returns null at one point. You could fix it by returning array(), but I instead checked to see if the return was null. – kainaw Jun 10 '16 at 20:01
Actually, as I didnt notice initially and @JoseManuelAbarcaRodríguez pointed out. This methodology does not work. It doesnt "fall back" enough – EyeOfTheHawks Jun 10 '16 at 20:03
Now the error is "Notice: Array to string conversion". kainaw, you are close to the solution. – Jose Manuel Abarca Rodríguez Jun 10 '16 at 20:16

Hierarchical Array Conversion to Flat Array

2 Answers2