Lesson 14 — Object-Oriented PHP

OOP: Classes and Objects

PHP fully supports object-oriented programming, letting you group related data and behaviour into classes, just as in languages like Java or C++.

Defining a Class

A PHP class groups properties (variables) and methods (functions) together, with the special __construct method running automatically whenever a new object is created.

PHP — A simple class 
class Student {
    public string $name;
    public int $age;

    public function __construct(string $name, int $age) {
        $this->name = $name;
        $this->age = $age;
    }

    public function introduce(): string {
        return "Hi, I'm {$this->name}, age {$this->age}";
    }
}

$s1 = new Student("Thandeka", 21);
echo $s1->introduce();

Common Mistakes

  • Forgetting the $this-> prefix when accessing a property or method from within the class itself.
  • Using -> to access properties/methods when => (array syntax) was intended, or vice versa.
  • Not declaring property visibility (public/private/protected), leaving intent unclear.
  • Forgetting the new keyword when creating an object from a class.

Professional Tip

Use $this->propertyName to access an object's own properties and methods from inside its class definition — forgetting $this is one of the most common early PHP OOP mistakes.

Your Turn

Create a Book class with title, author, and price properties, a constructor to set them, and a method that returns a formatted description string.

Mini Quiz

Which special method runs automatically whenever a new object is created from a PHP class?