PHP - Best Practices 2019

Daniel Opitz 06. December 2019

I think it’s time for a fresh and simplified blog post about the latest PHP Best Practices in 2019 / 2020. A lot has changed within the last time I have written about this topic in 2018.

Principles and rules

Here are the most important rules:

KISS - Keep it simple, stupid
YAGNI - You Arent Gonna Need It
DRY - Don’t repeat yourself
SOLID - The First 5 Principles of Object Oriented Design
The Boy Scout Rule - Leave your code better than you found it

Coding styles

Code must follow PSR-1 and PSR-12. PSR-2 is deprecated.
Add full PSR-5 DocBlocks for all classes and all methods.

Naming

Use english names only (class names, method names, comments, variables names, database table and field names, etc…).
Use class suffixes / prefixes according to PSR Naming Conventions.
Follow industry best practices for your directory and file structure:
- thephpleague/skeleton - A skeleton repository for packages
- pds/skeleton - Names for your root-level directories

Common rules

All methods must have type declaration and return type declaration.
Methods without return statement must declared with void as their return type.
Class properties must have typed properties (PHP 7.4+).
Don’t mix data types for parameters and return types, except for nullable.
Don’t extend classes or create abstract classes for the sake of “code reuse”, except for traits with test code only.
Create final classes by default, except you have to mock it (e.g. repositories).
Create private methods by default. Don’t create protected methods.
All method parameters must be used.

Dependency injection

Use composition over inheritance.
Declare all class dependencies only within the constructor.
Don’t inject the container (PSR-11). The service locator is an anti-pattern.
A constructor can accept only dependencies as object.
Scalar data types (string, int, float, array) are not allowed for the constructor. Pass them as parameter object.

Tools

Use a static code analyzer to detect bugs and errors. For example:

Daniel Opitz

Developer, Trainer & Open Source Contributor. Passionate about PHP, Slim Framework, and clean code.

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