Reverse flatted array to multidimensional - php

Question

In another thread i asked about flatten an array with a specific style to get something like this:
array(4) {
["one"]=> string(9) "one_value"
["two-four"]=> string(10) "four_value"
["two-five"]=> string(10) "five_value"
["three-six-seven"]=> string(11) "seven_value"
}
I've got some very good help there, but now im wondering how would i reverse this method to get again the same original array:
array(
'one' => 'one_value',
'two' => array
(
'four' => 'four_value',
'five' => 'five_value'
),
'three' => array
(
'six' => array
(
'seven' => 'seven_value'
)
)
)
I've tried with recursive method but with no luck.
I thank all the help in advance!

Answer 1

function expand($flat) {
$result = array();
foreach($flat as $key => $val) {
$keyParts = explode("-", $key);
$currentArray = &$result;
for($i=0; $i<count($keyParts)-1; $i++) {
if(!isSet($currentArray[$keyParts[$i]])) {
$currentArray[$keyParts[$i]] = array();
}
$currentArray = &$currentArray[$keyParts[$i]];
}
$currentArray[$keyParts[count($keyParts)-1]] = $val;
}
return $result;
}
Note that the code above is not tested and is given only to illustrate the idea.
The & operator is used for $currentArray to store not the value but the reference to some node in your tree (implemented by multidimensional array), so that changing $currentArray will change $result as well.

Answer 2

Here is an efficient recursive solution:
$foo = array(
"one" => "one_value",
"two-four" => "four_value",
"two-five" => "five_value",
"three-six-seven" => "seven_value"
);
function reverser($the_array) {
$temp = array();
foreach ($the_array as $key => $value) {
if (false != strpos($key, '-')) {
$first = strstr($key, '-', true);
$rest = strstr($key, '-');
if (isset($temp[$first])) {
$temp[$first] = array_merge($temp[$first], reverser(array(substr($rest, 1) => $value)));
} else {
$temp[$first] = reverser(array(substr($rest, 1) => $value));
}
} else {
$temp[$key] = $value;
}
}
return $temp;
}
print_r(reverser($foo));
strstr(___, ___, true) only works with PHP 5.3 or greater, but if this is a problem, there's a simple one-line solution (ask if you'd like it).