PHP - flatten a tree array into hierarchal CSV

Question

I have a tree structure array of departments and I need to flatten it out into a CSV (showing the full path to each end department)

Assume I have the following array:

$arr = array("AA" => ["BB" => [], "CC" => ["DD" => [], "EE" => []]], "FF" => ["GG" =>[]]);

var_dump:

array(2) {
  ["AA"]=>
  array(2) {
    ["BB"]=>
    array(0) {
    }
    ["CC"]=>
    array(2) {
      ["DD"]=>
      array(0) {
      }
      ["EE"]=>
      array(0) {
      }
    }
  }
  ["FF"]=>
  array(1) {
    ["GG"]=>
    array(0) {
    }
  }
}

I need them flattened into a CSV structure like this

AA
AA | BB
AA | CC
AA | CC | DD
AA | CC | EE
FF
FF | GG

I have tried recursive functions but I always end up with sub arrays which wont work as CSV

Are you the poster who popped the function up and then deleted it? Because whoever that was they got it first time! The CSV output was to help the front end guys with their product mapping - they wanted the CSV to be ordered like the tree but showing the full path to each department - I had tried similar recursive functions but always ended up getting sub arrays which I could flatten out! — Ben Duffin
– Ben Duffin, Commented May 8, 2019 at 10:54
I delete it as I found use case it fail - @BenDuffin - re-publish the answer — dWinder
– dWinder, Commented May 8, 2019 at 10:55

dWinder · Accepted Answer · 2019-05-08 10:51:26Z

2

Writing recursion function should be simple as:

function rec($arr, $pre) {
    foreach($arr as $k => $v) {
        $t = array_merge($pre, [$k]);
        echo implode (" | ", $t) . PHP_EOL;
        rec($v, $t);
    }
}

Simple example as:

$arr = array("AA" => ["BB" => [], "CC" => []], "DD" => []);
rec($arr, []);

Output:

AA
AA | BB
AA | CC
DD

answered May 8, 2019 at 10:51

dWinder

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1 Comment

Ben Duffin Over a year ago

Spot on - did exactly what I wanted. I am fine building stuff recursively into a tree structure but flattening it out seemed a lot harder - thank you!

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