Can you see anything wrong in the following image?

Persistent readers will notice that it’s part of the sidebar on this site’s main page, except slightly wrong. It turns out I have a bug that only occurs at the end of months! The following code is wrong:

date('F', mktime(0,0,0,$month))

The following code is right:

date('F', mktime(0,0,0,$month,1))

Why? It’s down to PHP being clever, and me being dumb (or possibly the other way round; it’s hard to tell with PHP).

The mktime function constructs a timestamp from the arguments you give it, filling in any missing arguments with the current local date and time. I guess this might be useful in some circumstances, but if you call it on, say, the 31st of October, when trying to use it to map 9 to September, the mktime function uses 31 for $day, and clearly there’s no such time as the 31st of September, so PHP decides to be clever by overflowing to the 1st of October. Similarly, attempting to map 2 to February when on the 31st of October overflows to the 3rd of March. Lovely.

The fix is to specify 1 for the day, since there’s always a first of the month.

The number one search result for “php get month name” currently recommends the wrong code. Google’s Code Search shows that this flawed idiom has already infiltrated a number of open source projects.

But now for the important part: there is a fixed version of my Wordpress theme!