Composer olmadan yapmanın yolunu buldum.

Bir Class Kodu;

<?php
<?php

class Markdown {
    public static $rules = array (
        '/(#+)(.*)/' => 'self::header',                           // headers
        '/\[([^\[]+)\]\(([^\)]+)\)/' => '<a href=\'\2\'>\1</a>',  // links
        '/(\*\*|__)(.*?)\1/' => '<strong>\2</strong>',            // bold
        '/(\*|_)(.*?)\1/' => '<em>\2</em>',                       // emphasis
        '/\~\~(.*?)\~\~/' => '<del>\1</del>',                     // del
        '/\:\"(.*?)\"\:/' => '<q>\1</q>',                         // quote
        '/`(.*?)`/' => '<code>\1</code>',                         // inline code
        '/\n\*(.*)/' => 'self::ul_list',                          // ul lists
        '/\n[0-9]+\.(.*)/' => 'self::ol_list',                    // ol lists
        '/\n(&gt;|\>)(.*)/' => 'self::blockquote ',               // blockquotes
        '/\n-{5,}/' => "\n<hr />",                                // horizontal rule
        '/\n([^\n]+)\n/' => 'self::para',                         // add paragraphs
        '/<\/ul>\s?<ul>/' => '',                                  // fix extra ul
        '/<\/ol>\s?<ol>/' => '',                                  // fix extra ol
        '/<\/blockquote><blockquote>/' => "\n"                    // fix extra blockquote
    );

    private static function para ($regs) {
        $line = $regs[1];
        $trimmed = trim ($line);
        if (preg_match ('/^<\/?(ul|ol|li|h|p|bl)/', $trimmed)) {
            return "\n" . $line . "\n";
        }
        return sprintf ("\n<p>%s</p>\n", $trimmed);
    }

    private static function ul_list ($regs) {
        $item = $regs[1];
        return sprintf ("\n<ul>\n\t<li>%s</li>\n</ul>", trim ($item));
    }

    private static function ol_list ($regs) {
        $item = $regs[1];
        return sprintf ("\n<ol>\n\t<li>%s</li>\n</ol>", trim ($item));
    }

    private static function blockquote ($regs) {
        $item = $regs[2];
        return sprintf ("\n<blockquote>%s</blockquote>", trim ($item));
    }

    private static function header ($regs) {
        list ($tmp, $chars, $header) = $regs;
        $level = strlen ($chars);
        return sprintf ('<h%d>%s</h%d>', $level, trim ($header), $level);
    }

    /**
     * Add a rule.
     */
    public static function add_rule ($regex, $replacement) {
        self::$rules[$regex] = $replacement;
    }

    /**
     * Render some Markdown into HTML.
     */
    public static function render ($text) {
        $text = "\n" . $text . "\n";
        foreach (self::$rules as $regex => $replacement) {
            if (is_callable ( $replacement)) {
                $text = preg_replace_callback ($regex, $replacement, $text);
            } else {
                $text = preg_replace ($regex, $replacement, $text);
            }
        }
        return trim ($text);
    }
}


echo Markdown::render ("# Başlık");
?>