Listing Recursif

<?php
error_reporting(E_ALL);
ini_set('display-errors',"on");


function get_arbo($inputArray){
  $max = count($inputArray);
  $tree = array();
  $flat = array();
  // Create a flat hierarchy array of all entries by their id
  for ($i = 0; $i < $max; $i++) {
    $n = $inputArray[$i];
    $id = $n['categorie_id'];
    $flat[$id] = $n;
  }
  // Then check all those entries by reference
  foreach ($flat as $key => &$child) {
    if (!isset($child['children']))
      $child['children'] = array();
      $id = $child['categorie_id'];
      $pid = $child['parent_id'];
      if ($pid > 0) {
        $flat[$pid]['children'][] = &$child;
      } else {
        $tree[$id] = &$child;
     }
  }
 return array_values($tree); 
}


function display($arr,$cat_parent="", &$out=array()){
  foreach($arr as $C){  
    $nom_categorie = !empty($C['nom_categorie']) ? $C['nom_categorie'] : $cat_parent;
    $children = !empty($C['children']) ? $C['children'] : NULL;
    $out[] = $cat_parent . " " . $nom_categorie;
    if(is_array($children)){
      display($children,$cat_parent . " " . $nom_categorie ,$out);
    }
  }  
}


$test = array();
$test[0]['parent_id'] = 0;
$test[0]['categorie_id'] = 18;
$test[0]['nom_categorie'] = "test";

$test[1]['parent_id'] = 0;
$test[1]['categorie_id'] = 20;
$test[1]['nom_categorie'] = "test2";


$test[2]['parent_id'] = 18;
$test[2]['categorie_id'] = 21;
$test[2]['nom_categorie'] = "test3";

$test[3]['parent_id'] = 21;
$test[3]['categorie_id'] = 22;
$test[3]['nom_categorie'] = "test33"; 


display(get_arbo($test),"",$out);
echo "<pre>";
print_r($out);
echo "</pre>";

// $tonArray => ton array

$newarray = array();
foreach($tonArray as $R){
  $newarray [$R['parent_id']][$R['categorie_id']] = $R['nom_categorie'];
}

echo "<pre>";
print_r($newarray);
echo "</pre>";

$result = get_arbo($test);

function get_arbo($inputArray){
  $max = count($inputArray);
  $tree = array();
  $flat = array();
  // Create a flat hierarchy array of all entries by their id
  for ($i = 0; $i < $max; $i++) {
    $n = $inputArray[$i];
    $id = $n['categorie_id'];
    $flat[$id] = $n;
  }
  // Then check all those entries by reference
  foreach ($flat as $key => &$child) {
    if (!isset($child['children']))
      $child['children'] = array();
      $id = $child['categorie_id'];
      $pid = $child['parent_id'];
      if ($pid > 0) {
        $flat[$pid]['children'][] = &$child;
      } else {
        $tree[$id] = &$child;
     }
  }
 return array_values($tree); 
}

<?php 
$res= array();
for( $i =0; $i<$test.length; $i++){
	$res[$i] = $test[$i]['nom_categorie'];
}
?>