I was recently asked by one of my readers to give feedback on the following article he read: 10 Most Common PHP Mistakes. It is well written and very thorough. Most of the tips are specific to PHP, others are about web programming in general or database performance. It's a very good read. I was also asked to contribute to this list, so here are 7 more tips.
Her list of seven touches on topics like caching, allowing SQL injection, disabling error reporting and ignoring accessibility. She also includes some configuration settings, code and links to other tools/resources to help provide information on preventing these other mistakes.