"Cross-over" developers out there (those that use PHP and Javascript on a regular basis) can sometimes get confused by little syntax things. Stoyan Stefanov got tripped up by just such an issue.
The front-end developer is a strange beast who has to jiggle to and fro and code in several languages literally at the same time - javascript, html, css, php or some other server side language, some SQL dialect... No wonder that sometimes we make silly mistakes.
His issue was with appending - in Javascript, it's a plus but in PHP, it's a period. Unfortunately, the problem can be hard to track down since Javascript also has a use for the period operator - treating the preceding thing like an object.