Short answer, weird markdown parsing issue. I had to create a blank line between “Which prints” and your “```php” code block. Don’t ask me why that impacted the link, not 100% sure. I do know that eventually Discourse will get a new markdown parser, it just isn’t ready yet.
Also, apologies for it taking so long for me to investigate. I’ve had a busy couple of weeks and just now had the time to give this topic the attention it deserved.