Class for dumping/beautifying JSON

JsonDumper.class.php

<?php

class JsonDumper
{
    /** @var string */
    private $json;

    /** @var int  spaces to use for one indentation level */
    private $indentation;

    public function __construct($json, $indentation = 4) {
        // TODO: check if json is valid first

        $this->json = $json;
        $this->indentation = $indentation;

        $this->process();
    }

    private function process() {
        $pos = 0;
        $currentIndent = 0;

        while (($nextPos = $this->getNextToken($pos)) !== false) {
            $newLine = true;

            // if a token is at current position
            if ($nextPos === $pos) {
                $token = $this->json[$pos];

                if ($token == '}' || $token == ']') {
                    $currentIndent -= $this->indentation;
                    $newLine = false;
                    echo "\n", str_repeat(' ', $currentIndent);
                } elseif ($token == '{' || $token == '[') {
                    $currentIndent += $this->indentation;
                }

                echo $token;

                if ($token == ':') {
                    $newLine = false;
                    echo ' ';
                }

                $pos++;
            }

            if ($newLine) {
                echo "\n", str_repeat(' ', $currentIndent);
            }

            $nextPos = ($this->getNextToken($pos) !== false) ? $this->getNextToken($pos) : strlen($this->json);
            echo substr($this->json, $pos, $nextPos - $pos);

            $pos = $nextPos;
        }
    }

    private function getNextToken($currentPos) {
        $tokens = '{}[]:,';
        $regex = preg_quote($tokens);

        preg_match("/[$regex]/", $this->json, $matches, PREG_OFFSET_CAPTURE, $currentPos);

        if (isset($matches[0][1])) {
            return $matches[0][1];
        } else {
            return false;
        }
    }
}