In this new post from Vidyut Luther on PHPCult.com, he mentions some difficulties he had installing some new PHP software - caused by bad habits the programmers used that caused trouble down the line. To help prevent further abuses of these issues, he lists out some of them.

His list so far is:

• Turning "register globals" on
• using shot open tags
• using the ASP style of tagging
• single-line condition statements (without the curly braces)
• improper use of exit()
• assuming settings on a remote server

For each of the above options, he briefly covers his opinion as to why they're wrong and can cause some serious headaches down the line. Most advanced programmers out there know about most of these issues, and have learned to work without them.