Hockey

There are entire books devoted to this topic. 1) Familiarize yourself with design patterns 2) Start by sketching your GUI on paper - try and discover any caveats 3) Using your visual GUI sketches, start designing your DB schema - normalize it. 4) Begin coding your HTML templates based on your visual sketches 5) Begin developing the model code 6) Begin tying your interface to your model. 7) When step 6 becomes to complex refactor into proper MVC separations. Reapt until finished and voila - a complete product

1) Look into MVC + 1 2) Avoid heredoc syntax 3) Start using a template engine It's one thing to mass applicaiton logic with business/domain/model logic but it's the WORST when people mingle HTML with PHP...that gets horribly messy super fast. Change that pronto.

The other questions are hard to answer without better/deeper understanding of your system and it's architecture. #2: Use a registry - especially if it's initialize in the application entry point. I Use the registry for strictly that purpose giving global access to centralized objects. Authentication Database etc, etc...