Knockout-Lite/app/Helper/BBCode.php

<?php

namespace App\Helper;

// formatting
use App\BbCode\Tag\Unknown;
use App\BbCode\Tag\Text;
use App\BbCode\Tag\Bold;
use App\BbCode\Tag\Italic;
use App\BbCode\Tag\Underline;
use App\BbCode\Tag\Strikethrough;
use App\BbCode\Tag\Spoiler;
use App\BbCode\Tag\HeadingOne;
use App\BbCode\Tag\HeadingTwo;
use App\BbCode\Tag\Link;
use App\BbCode\Tag\Code;
// quotes
use App\BbCode\Tag\Quote;
use App\BbCode\Tag\Blockquote;
// embeds
use App\BbCode\Tag\Image;
use App\BbCode\Tag\Twitter;
use App\BbCode\Tag\Youtube;
use App\BbCode\Tag\Video;

use Knockout\BbCode\BbCode as Parser;
use Knockout\BbCode\Tokenizer\Tokenizer;

class BBCode {

    private $tokens;

    public function __construct($content)
    {
        $this->tokens = (new Tokenizer())->tokenize($content);
    }

    public function render()
    {
        $parser = new Parser();

        $unknown = new Unknown();
        $parser->addTag($unknown);

        $text = new Text();
        $parser->addTag($text);

        $bold = new Bold();
        $parser->addTag($bold);

        $italic = new Italic();
        $parser->addTag($italic);

        $underline = new Underline();
        $parser->addTag($underline);

        $strikethrough = new Strikethrough();
        $parser->addTag($strikethrough);

        $image = new Image();
        $parser->addTag($image);

        $link = new Link();
        $parser->addTag($link);

        $code = new Code();
        $parser->addTag($code);

        $quote = new Quote();
        $parser->addTag($quote);

        $blockquote = new Blockquote();
        $parser->addTag($blockquote);

        $twitter = new Twitter();
        $parser->addTag($twitter);

        $youtube = new Youtube();
        $parser->addTag($youtube);

        $video = new Video();
        $parser->addTag($video);

        $tags = [
            $unknown,
            $text,
            $bold,
            $italic,
            $underline,
            $strikethrough,
            $image,
            $link,
            $code,
            $quote,
            $blockquote,
            $twitter,
            $youtube,
            $video
        ];

        $anyChild = [
            $bold,
            $quote,
            $blockquote,
            $text,
            $unknown
        ];

        foreach ($anyChild as $parent) {
            foreach ($tags as $tag) {
                $parser->addAllowedChildTag($parent, $tag);
            }
        }

        return $parser->format($this->tokens);
    }

}