Online PHP editor | output for K246b

<?php $input = 'RA(B(CCC)B(CC))PA(BB(C))D'; abstract class Component { public $letter; public function __construct($letter) { $this->letter = $letter; } public function dump($level = 0) { echo str_repeat("&emsp;", $level).$this->letter."\n"; } } class Leaf extends Component {} class Node extends Component { /** @var Component[] */ private $items = []; private static function findComponentsFromInput($input) { $numOpenBrackets = false; $numClosedBrackets = false; $trimPositions = []; $lastTrimPosition = 0; for ($currentCharNumber = 0, $strLen = strlen($input); $currentCharNumber < $strLen; $currentCharNumber++) { if ($input{$currentCharNumber} == '(') { $numOpenBrackets = (int)$numOpenBrackets + 1; } elseif ($input{$currentCharNumber} == ')') { $numClosedBrackets = (int)$numClosedBrackets + 1; } $isLeaf = $numOpenBrackets === false && $numClosedBrackets === false && (!isset($input{$currentCharNumber + 1}) || $input{$currentCharNumber + 1} != '('); if ($isLeaf) { $trimPositions[] = [ "type" => 'leaf', "start_trim" => $lastTrimPosition, "trim_length" => $currentCharNumber - $lastTrimPosition + 1 ]; $lastTrimPosition = $currentCharNumber + 1; } $isNode = is_int($numOpenBrackets) && is_int($numClosedBrackets) && $numOpenBrackets - $numClosedBrackets == 0; if ($isNode) { $numOpenBrackets = false; $numClosedBrackets = false; $trimPositions[] = [ "type" => "node", "start_trim" => $lastTrimPosition, "trim_length" => $currentCharNumber - $lastTrimPosition + 1 ]; $lastTrimPosition = $currentCharNumber + 1; } } $resultComponents = []; foreach ($trimPositions as $trimPosition) { $resultComponents[] = [ "type" => $trimPosition["type"], "data" => substr($input, $trimPosition["start_trim"], $trimPosition["trim_length"]) ]; } return $resultComponents; } public function createComponentsFromInput($dataString) { $components = self::findComponentsFromInput($dataString); foreach($components as $component) { if($component['type'] == 'leaf') { $this->addItem(new Leaf($component['data'])); } elseif($component['type'] == 'node') { preg_match('~(\w)*$(.+)$~', $component['data'], $matches); if(!isset($matches[1]) || !isset($matches[2])) { echo "Wrong input format"; exit; } $newNode = new Node($matches[1]); $newNode->createComponentsFromInput($matches[2]); $this->addItem($newNode); } } return $this; } public function addItem(Component $item) { $this->items[] = $item; } public function dump($level = 0) { if($this->letter == 'root') { $newLevel = $level; } else { parent::dump($level); $newLevel = $level + 1; } foreach($this->items as $item) { $item->dump($newLevel); } return $this; } } $root = new Node("root"); $root->createComponentsFromInput($input)->dump();