sorting chapters in an 4 level array - php

Question

I want to sort an existing array into 4 dimension array:
the "list" array that I have:
1 => "text1"
10 => "text10"
11 => "text11"
101 => "text101"
1011 => "text1011"
10123 => "text10123"
2 => "text2"
20 => "text20"
201 => "text201"
2011 => "text2011"
20111 => "text20111"
the array I want is one that has all the data sorted by each number (in 4 dimention) i mean that i won't have an other array in the end of $chapter[1] containing 10123 => "text10123" (this one will be in the same array as this one : 1011 => "text1011"
here is an exemple of the array i want
$chapter[1] = array(
1 => "text1", array(
10 => "text10", 11 => "text11", array(
101 => "text101", array(
1011 => "text1011", 10123 => "text10123" )
)
)
);

Answer 1

I guess you can use for-loop and break each number to digits (with str-split) and then add the arrays.
Consider the following example:
$arr = array(1, 11, 111, 113, 2, 21, 211, 213);
$chapter = array(); // this will be your result array
foreach($arr as $e) {
$digits = str_split($e);
$current = &$chapter;
foreach($digits as $d) {
if (!isset($current[$d]))
$current[$d] = array();
$current = &$current[$d];
}
}
Notice I used & to assign the new array to the original result one.
I know your array has missing key and not have to be sorted but I guess you can overcome it (filter and sort the array before)
Edited
After question has change this is the example code: (when key DATA is for the text you want and key CHILDREN for the next elements)
$arr = array(1 => "text1", 10 => "text10", 11 => "text11", 101 => "text101", 1011 => "text1011", 10123 => "text10123", 2 => "text2", 20 => "text20", 201 => "text201", 2011 => "text2011", 20111 => "text20111");
$chapter = array();
foreach($arr as $key => $val) {
$digits = str_split(substr($key, 0, 4)); // if 4 digits is the max depth
$current = &$chapter;
foreach($digits as $d) {
if (!isset($current["CHILDREN"][$d]))
$current["CHILDREN"][$d] = array();
$current = &$current["CHILDREN"][$d];
}
$current["DATA"] = $val;
}