PHP how to convert an single array to multidimentional array? - php

Question

I have that single array and I need to convert in a multidimensional array without using array_merge, array_replace_recurcive etc, just an autonomous function:
$single = [
0 => 'one',
1 => 'two',
2 => 'tree',
3 => 'four',
4 => 'five'
];
And convert to look like this, with the last key as value:
$multidimentional = [
'one' => [
'two' => [
'tree' => [
'four' => 'five'
]
]
]
];
I have create a recursion function if this helps:
function array_replace_recursive($defaults, $replaces) {
if(is_null($replaces)) {
$replaces = [];
}
if(!is_array($defaults) || !is_array($replaces)) {
return $replaces;
}
foreach($defaults as $key => $value) {
if(!array_key_exists($key, $replaces) || is_null($replaces[$key])) {
$replaces[$key] = $value;
} else {
if(is_array($replaces[$key]) && is_array($value)) {
$replaces[$key] = array_replace_recursive($replaces[$key], $value);
}
}
}
return $replaces;
}

Answer 1

You can do this with PHP (as of 5.6) argument unpacking and a very simple recursive function:
$single = [
0 => 'one',
1 => 'two',
2 => 'tree',
3 => 'four',
4 => 'five'
];
function convert($key, ...$values) {
if (count($values) == 1)
return array($key => $values[0]);
else
return array($key => convert(...$values));
}
print_r(convert(...$single));
Output:
Array
(
[one] => Array
(
[two] => Array
(
[tree] => Array
(
[four] => five
)
)
)
)
You can also do it without using count (only isset):
function convert2($key, ...$values) {
if (!isset($values[1]))
return array($key => $values[0]);
else
return array($key => convert(...$values));
}
print_r(convert2(...$single));
Output:
Array
(
[one] => Array
(
[two] => Array
(
[tree] => Array
(
[four] => five
)
)
)
)

Answer 2

Thinking in recursion, you can write a base case that returns the value of the currently seen item if it is one less than the length of the array.
$singleDim = [
0 => 'one',
1 => 'two',
2 => 'tree',
3 => 'four',
4 => 'five'
];
function toMultiDimArray($arr, $seen=0) {
if ([] === $arr) {
return [];
}
if(count($arr) - 1 === $seen) {
return $arr[$seen];
}
return [
$arr[$seen] => toMultiDimArray($arr, $seen+1)
];
}
$multiDim = toMultiDimArray($singleDim);
var_dump($multiDim);
array(1) {
["one"]=>
array(1) {
["two"]=>
array(1) {
["tree"]=>
array(1) {
["four"]=>
string(4) "five"
}
}
}
}

Answer 3

$single = [
0 => 'one',
1 => 'two',
2 => 'tree',
3 => 'four',
4 => 'five'
];
function to_multidimentional($array, $count = 0, $seen = 0) {
if($count - 1 === $seen) {
return $array[$seen];
}
return [
$array[$seen] => to_multidimentional($array, $count, $seen + 1)
];
}
$single = to_multidimentional($single, count($single));
print_r($single);
exit;

Answer 4

There's nothing recursive about this. It's just iterating over the $single array backwards and then embedding the result inside the new key each time:
function foo( $single ) {
$multidimensional = [ $single[ count($single) - 1 ] ];
for( $i = count($single) - 2; $i >= 0; $i-- ) {
$multidimensional = [ $single[$i] => $multidimensional ];
}
}