Convert a flat array to a hierarchical multidimensional array

Question

I have a standard array with key-value pairs - and I want to use keys to convert it to a multidimensional array. The difficulty seems to be that I need to recursively quote an unknown number of new keys and turn them into a multidimensional array. In short, I want this:

$val[alfa.xray.uno] = "Some value"; => $val['alfa']['xray']['uno'] = "Some value"; 

Example: (The code does not work and should also handle N measurements, but you get the idea ..)

 $arr['alfa.xray.uno'] = "Alfa X-Ray Uno"; $arr['alfa.yaho.duo'] = "Alfa Yaho Duo"; $arr['beta.xray.uno'] = "Beta X-Ray Uno"; $arr['beta.xray.duo'] = "Beta X-Ray Duo"; $arr['just-me'] = "Root-level item"; print_r( array_flat_to_multidimensional($arr) ); function array_flat_to_multidimensional($arr) { foreach($arr as $key=>$val) { $key = explode(".",$key); for($i=0; $i<count($key); $i++) { if($i==0) { $out[$key[$i]] = $val; } else if($i==1) { $out[$key[$i-1]][$key[$i]] = $val; } else if($i==2) { $out[$key[$i-2]][$key[$i-1]][$key[$i]] = $val; } else if($i==3) { $out[$key[$i-3]][$key[$i-2]][$key[$i-1]][$key[$i]] = $val; } } } return $out; } 

Perhaps RecursiveArrayIterator will do the trick?

Answer 1

You can use links to iterate through it and create a structure of nested arrays:

 $out = array(); foreach ($arr as $key=>$val) { $r = & $out; foreach (explode(".", $key) as $key) { if (!isset($r[$key])) { $r[$key] = array(); } $r = & $r[$key]; } $r = $val; } return $out; 

Answer 2

use Luke recursion

 function ins(&$ary, $keys, $val) { $keys ? ins($ary[array_shift($keys)], $keys, $val) : $ary = $val; } // test $arr['alfa.xray.uno'] = "Alfa X-Ray Uno"; $arr['alfa.yaho.duo'] = "Alfa Yaho Duo"; $arr['beta.xray.uno'] = "Beta X-Ray Uno"; $arr['beta.xray.duo'] = "Beta X-Ray Duo"; $arr['just-me'] = "Root-level item"; $a = array(); foreach($arr as $k => $v) ins($a, explode('.', $k), $v); print_r($a); 

Answer 3

You can use reference when walking through hierarchical levels of an array:

 function array_flat_to_multidimensional($arr) { $out = array(); foreach ($arr as $compondKey => $val) { $ref = &$out; foreach (explode(".", $compoundKey) as $key) { if (!array_key_exists($key, $ref)) $ref[$key] = array(); $ref = &$ref[$key]; } $ref = $val; } unset($ref); return $out; }