Hello there!

Who am I?

Yoan-Alexander GrigorovPHP developer (with pride!)Software EngineerCriticDesign Patterns adventurer

SOLID design?

Imagine code as a painting

Well... maybe not this one in particular!

Now that's better!

Nothing against modern art, but...

Code should be easy to recognize!

How a project starts:

Several months later...

What is going wrong?

Frequently logic changes are made with hacks without refactoring

Lack of knowledge on stuff

Lack of discipline

SOLID? What's that?

Single responsibility

Open-closed

Liskov substitution

Interface segregation

Dependency inversion

What SOLID can't do?

Cure ebola

Explain why is there PHP 7 coming out, but no PHP 6?!?!?

Make Bulgarian politicians suck less

Let's break it down!

Single responsibility principle

Every variable, class, function, etc. should have a single responsibility, described in it's name (if any).

Single responsibility principle

Basically it's bad if we have a function (or class) that does more then what it's name says.

Single responsibility principle

Here is one real-life example how bad it is to break this rule:

Single responsibility principle

Hidden features can have unexpected effects

Single responsibility principle

Bad code example: