A programmer reports this problem when using PHP: “In NetBeans and (I’m assuming) most other development environments, the project folder and the server source folders must have the same name, or the...

A programmer reports this problem when using PHP: “In NetBeans and (I’m assuming) most other development environments, the project folder and the server source folders must have the same name, or the program won’t work. I discovered this by accident when I was trying to create my project for the umpteenth time.” What kind of error is it? What rules were applied, and which should have been applied earlier?