Online PHP editor | refs for T2Rba

<?php $groupList = [ [ 'id' => 1, 'parent_id' => null, 'category' => null, 'children_list' => [ [ 'id' => 3, 'parent_id' => 1, 'category' => null, ], [ 'id' => 4, 'parent_id' => 1, 'category' => 'Category number 20', 'children_list' => [ [ 'id' => 7, 'parent_id' => 4, 'category' => null, ], [ 'id' => 8, 'parent_id' => 4, 'category' => 'Category number 30', ], ], ], ], ], 'id' => 2, 'parent_id' => null, 'category' => null, 'children_list' => [ [ 'id' => 5, 'parent_id' => 2, 'category' => null, 'children_list' => [ [ 'id' => 6, 'parent_id' => 5, 'category' => null, ], ], ], ], ]; $filter = array_map(function ($n){return f($n);}, $groupList[0]); echo '<pre>'; print_r($filter); function f(&$a){ foreach($a as $k=>&$r){ if(!$r['category']) unset($a[$k]); if($r['children_list']) $r['children_list']=f($r['children_list']); } return $a; }