Build multidimensional array from keys - php

Question

I can't seem to figure this out and I'm hoping someone has a magical recursive solution to this. I have a list of keys and basically I want to transform it into a nested array.
array('level1', 'level2', 'level3');
To
array(
'level1' => array(
'level2' => array(
'level3' // last key in array should be just a value
)
)
)
Much appreciation to anyone who can help!

Answer 1

Something like this should do the job:
function buildMultiDimensional(Array $arr)
{
// the first value will become a new key
$newKey = array_shift($arr);
if (empty($arr)) {
// this is where the recursion stops
return $newKey;
}
// and the recursion !!!
return array($newKey => buildMultiDimensional($arr));
}
$arr = array('level1', 'level2', 'level3', 'level4', 'level5');
var_dump(buildMultiDimensional($arr));
The result is what's expected:
array(1) {
["level1"]=>
array(1) {
["level2"]=>
array(1) {
["level3"]=>
array(1) {
["level4"]=>
string(6) "level5"
}
}
}
}

Answer 2

You don't need recursion. A single loop is fine with references.
<?php
//array to iterate
$array = array('level1', 'level2', 'level3');
//contains our entire array
$out = array();
//temp variable to store references as we go down.
$tmp = &$out;
//get the last value off the array
$last = array_pop($array);
//loop over the array
foreach($array as $level){
//make an array under the current level
$tmp[$level] = array();
//assign tmp to the new level
$tmp = &$tmp[$level];
}
//assign the last key as the value under the last key
$tmp = $last;
//display output
print_r($out);
example: http://codepad.viper-7.com/zATfyo
And without references, working in reverse:
<?php
//array to iterate
$array = array('level1', 'level2', 'level3');
//get the last value off the array
$out = array_pop($array);
//flip the array backwards
$array = array_reverse($array);
//loop over the array
foreach($array as $level){
$out = array($level=>$out);
}
//display output
print_r($out);
Example: http://codepad.viper-7.com/fgxeHO