In this recent article Kevin Waterson brings up a point that needs to be addressed (not just in the PHP world, but in all other programming communities around the web) - the quality and accuracy of the tutorials that are posted.
In a recent series of tutorials released by SUN Developers Community a few notable omissions glared back from the web page. Like many PHP tutorials that pollute the web, there was a little, or no error checking, or error handling in the provided code examples. [...] The tutorial in question, brings to light the need for tutorial writers and PHP authors to provide not only the basics of the subject being presented, but also how to handle errors when things go wrong.
Kevin reinforces the fact that, despite the author stating that all input would always be well-formed, there's no reason to dismiss error reporting because of it. There's still things that can go wrong even if the data is exactly how you assume it to be. He reinforces the idea that tutorials, by their nature, should teach proper coding techniques, including proper error reporting and filtering.