UML I've found saves a lot of time as well. You can begin to visualise everything before you even create your first PHP document. You've got it all down in a document on how it all works and you've cleared up any issues that were identified in your proposed implementation. That way once you've ironed out all the creases, you won't have to start editing your code, although there will always be times mid-code where you realise something can be done better and more efficiently.

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The man who comes back through the Door in the Wall will never be quite the same as the man who went out.