Question

How to use single-level inheritance in PHP

Answer 1

class A {
    public function print_s($s) {
        echo $s . "\n"; 
    } 
    public function print_() {
        echo 'class A' . "\n"; 
    }
}
class B extends A {
    public function print_s($s) {
        echo $s . "\n"; 
    }
    /*public function print_() {
        echo "class B" . "\n"; 
    }*/
}


$a = new A();
$b = new B();
 
$a->print_s('class A - php');
$a->print_();       
 
$b->print_s('class B - java'); 
$b->print_();       


 
/*
run:
 
class A - php
class A
class B - java
class A
 
*/
 

 

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Answer 2

// Basic single‑level inheritance

class Animal {
    public function speak() {
        return "Some generic sound";
    }
}

class Dog extends Animal {
    public function bark() {
        return "Woof!";
    }
}

$dog = new Dog();
echo $dog->speak(); // inherited
echo "\n";
echo $dog->bark();  // child-specific


 
/*
run:
 
Some generic sound
Woof!
 
*/
 

 

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Answer 3

// Overriding a parent method

class Animal {
    public function speak() {
        return "Some generic sound";
    }
}

class Cat extends Animal {
    public function speak() {
        return "Meow";
    }
}

$animal = new Animal();
$cat = new Cat();

echo $animal->speak(); // Some generic sound
echo "\n";
echo $cat->speak();    // Meow


 
/*
run:
 
Some generic sound
Meow
 
*/
 

 

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