<?php $re = '/(?<=\(|^)([^()]*)/'; $str = "0A,0B(1A((3A, 3B, 3C)))"; foreach ($matches[1] as $m){ }
Standard input is empty
Array ( [0] => Array ( [0] => 0A [1] => 0B ) [1] => Array ( [0] => 1A ) [2] => Array ( [0] => ) [3] => Array ( [0] => 3A [1] => 3B [2] => 3C ) )