Abstract class vs Interface (In PHP)

test.md

Abstract Class	Interface
A method must be declared as abstract. Abstract methods doesn't have any implementation	All methods, by default are abstract methods only. So, one cannot declare variables or concrete methods in interfaces
Abstract methods can be declared with access modifiers like public, private, protected. When implementing in subclass these methods must be defined with the same visibility	All methods in an interface must be declared public
Abstract class can contain variables and concrete methods	Interface cannot contain variables and concrete methods, except constants
A class can inherit only one abstract class ( multiple inheritance is not possible )	A class can implement, many interfaces ( multiple inheritance is possible )

e.g:

Abstract class

abstract class MotorVehicle
{
    int fuel;
    int getFuel()
    {
        return this.fuel;
    }
    abstract void run();
}

class Car extends MotorVehicle
{
    void run()
    {
        print("Vroom");
    }
}

Interface

interface MotorVehicle
{
    int getFuel();
    void run();
}

class Car implements MotorVehicle
{
    int fuel;
    
    void run()
    {
        print("Vroom");
    }

    int getFuel()
    {
        return this.fuel;
    }
}