Array
(
    [1] => Array
        (
            [id] => 1
            [title] => Компьютеры, Ноутбуки, Планшеты
            [parent] => 0
            [leaf] => 1
            [childs] => Array
                (
                    [105187] => Array
                        (
                            [id] => 105187
                            [title] => Компьютеры
                            [parent] => 1
                            [leaf] => 1
                            [childs] => Array
                                (
                                    [104978] => Array
                                        (
                                            [id] => 104978
                                            [title] => Компьютеры Acer
                                            [parent] => 105187
                                            [leaf] => 1
                                        )

public function not_child($tree)
{
     $catlist=array();
     foreach($tree as $one)
        {
          if(!isset($one['childs']) )
            {
                array_push($catlist,$one['id']);
                //echo $one['id'].'<br>';
                
            }  
          else
            {
               $this->not_child($one['childs']);
            }  
        }

return $catlist;
echo '<pre>'.print_r($catlist,true).'</pre>'; 
}