There's been a few articles posted on various blogs in the PHP community recently about the "most correct" usage of the "private" scope in your PHP applications. As with any feature of just about any language out there, there's people on both sides of the fence. Here's the ones that have weighed in so far:

• Brandon Savage's initial post (an excerpt from his upcoming "Do This, Not That" book)
• A response to this from Anthony Ferrara
• Brandon's own response to comments on his previous article
• This new post from Larry Garfield and some of his experience from the Drupal world

Various topics come up during these posts including static coupling, using interfaces versus inheritance, wrapper classes and developer intent.