I know the following works to share a link to FB:
https://www.facebook.com/sharer/sharer.php?u=http://rot47.net/picture-gallery/categories.php
But, this also works:
https://www.facebook.com/sharer/sharer.php?u=http%3A%2F%2Frot47.net%2Fpicture-gallery%2Fcategories.php
If both works, why should we use urlencode in PHP??