Single inheritance, a class inherits properties and methods from only one parent class.

<?php 
class ParentClass 
{ 
	/* Parent class definition */
}
class ChildClass extends ParentClass
{ 
	/* Child class extending ParentClass */
}
?>

Example:

<?php
// Parent class
class Vehicle {
    public function start() {
        echo "Vehicle started.";
    }
}

// Child class inheriting from the parent class
class Car extends Vehicle {
    public function accelerate() {
        echo "Car is accelerating.";
    }
}

// Create an object of the child class
$obj = new Car();

// Accessing both class parent and child method
$obj->start();       // Output: Vehicle started.
$obj->accelerate();  // Output: Car is accelerating.
?>

• The Vehicle class is the parent class.
• The Car class is a child class inheriting from Vehicle.
• The Car class inherits the start() method from the Vehicle class.
• The Car class also has its own method accelerate().
• When we create an object of the Car class, we can access methods from both the parent and child classes.