On PHPFreaks.com they have a new "top ten" list of signs to look out for to tell if you're dealing with crappy software or not.

Like it or not, as a professional developer, sooner or later you are going to do some customising (if you are lucky, "extending") of existing software. If you are not familiar with the software, it is good advice to look into it before accepting the job. I had to learn that the hard way. But how do you recognize crappy applications without getting knee deep into the code?

Their list of signs include:

• The software tries to reinvent the object model, or "fix" language features.
• Scattered HTML and SQL
• Multiple levels of inheritance
• In the code base, there is a directory called "core"