Object-Oriented PHP · Lesson 2 of 14

Classes

Declare a class as a reusable blueprint for objects.

Lesson

A class declares properties and methods that define a kind of object. Keep its public interface small and use visibility to protect invariants. Class names conventionally use PascalCase, and Composer autoloading lets each class live in a predictable file. The example declares a class with a typed public operation. Further guidance Give an object one clear responsibility and protect state that must satisfy a rule. Prefer a small public contract and composition for replaceable collaborators; use inheritance only for a genuine subtype. Test behavior through public methods instead of relying on internal implementation details. Practice task: Create a fresh example for Classes. Predict the result before running it, then change one input and explain why the result changes. Test a normal case and one boundary or invalid case where it applies. Compare your output with the example and note one rule you would use in a real project.

Code examples

Classes

PHP

class Greeter
{
    public function greet(string $name): string
    {
        return "Hello, $name";
    }
}
echo (new Greeter())->greet('Ari');

Expected output

Hello, Ari

Key points

Declare a class as a reusable blueprint for objects.
Protect object invariants behind a small public API.
Prefer composition unless inheritance expresses a genuine subtype.

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