I set page content type to Content-Type: text/markdown, output string should be bold but it's shown the raw string : **bold**
These are HTTP headers:
HTTP/1.1 200 OK
Cache-Control: no-cache
Connection: Keep-Alive
Content-Type: text/markdown; charset=UTF-8
Date: Tue, 12 Nov 2013 17:30:35 GMT
Keep-Alive: timeout=5, max=100
Server: Apache/2.4.3 (Win32) OpenSSL/1.0.1c PHP/5.4.7
Set-Cookie: laravel_session=qf3bsgt8l2ao97vh9650mq9e30; expires=Tue, 12-Nov-2013 19:30:35 GMT; path=/; httponly
Transfer-Encoding: chunked
X-Powered-By: PHP/5.4.7
I also used text/x-markdown although it's deprecated.
Web browsers don't understand Markdown syntax natively. You need to use a Markdown parser library to convert your markup to HTML.
There are a whole ton to choose from. Here is a good starting point for PHP:
http://michelf.ca/projects/php-markdown/
From your cookie header it looks like you're using the Laravel framework? In that case you probably want to look at the ready made bundles:
http://bundles.laravel.com/search/tag/Markdown
If you don't want to do this server-side, you could also convert your content with javascript: