I believe understanding the patterns in your own thinking will by far make the biggest impact on how good you will get as a programmer. Forget design patterns, forget unit testing, forget all those functions you know. Important is to question why they exist and how they could be improved.

He illustrates through a few examples what he means. He describes one such thought method, the "return home early" process - basically, if something looks too complex for its own good, it probably is. He offers a different way of thinking about it too, a more visual way that can help simplify things even more by laying out the pieces and seeing where they all fit.

The method which we used to count number of friends of a specific user who has added that application was returning 1 when there is no friend actually installed it.

He gives the SQL query and the PHP code he was originally using to find out the number of users for the application. The problem came from the fact that the returning value wasn't an array - it was a string. The corrected code (that checks for array-ness) is also included.